פירוש על עירובין 5:12

כיצד מעברין (how do they extend the city limits -for defining the Sabbath limit) – the language of a pregnant woman whose belly protrudes. And this is what he said, how does she have the extension of the city limits? If one house enters, and another house leaves, etc. And when he comes to put up a marker as a sign of the boundary of the city and he comes to measure two-thousand [cubits] outside it. But if hits wall was not part of it but rather the near-by houses and they were connected, and there is a house that enters into the city more than its neighbor, and its entrance appears defective, and there is house that protrudes and goes out side more than its neighbor.

Introduction The Hebrew word for “extensions” here is the same word used to extend the month (from 28 to 29 days) and to extend the year (from 12 to 13 months). The “extensions” to the city are critical when figuring out how far the Shabbat limit goes. Before we reckon the 2000 cubits around the city, we must first delineate exactly what is included in the city.

או פגום נכנס פגום יוצא – there are towers protrude in the wall, sometimes they protrude inwards and sometimes outwards.

How do they make extensions for cities [for the purpose of defining the Shabbat limit]?
If one house recedes and another projects, If at the end of the city there is a row of houses, but the row is not set up evenly, the Shabbat limit is measured from the house that projects the most and not from the house that recedes.

או שהיו שם – at one of the corners of the city.

Or if one turret [of the wall] recedes and another projects, If there is part of the wall (such as a turret, a tower used to guard the city) which projects further than other parts, the Shabbat limit is measured from the further projection.

גדודיות גבוהות (ruins/debris – ten handbreadths high) – broken parts of the wall of the destroyed homes, and there are within seventy cubits and remnants of the city.

If there were ruins ten handbreadths high, or bridges, or sepulchral monuments that contained dwelling places, they extend the boundary of the town is to include them. If there were ruins outside the parts of the city, or bridges or structures made over graves, then all of these are also included in the city.

או נפשות (structure next to or over a tomb) – a building that they make on the grave, and it has within them a dwelling house.

And they make it [the Shabbat limit] like a square tablet in order that the use of the corners might be gained. When they come to set the Shabbat limit, the first thing they do is make the city into a rectangle, with the furthest structure on each side being the city’s limits. Even if the city is circular, they draw a rectangle around it, so that people get some extra place to travel at the corners. The 2000 cubits are now measured in a square around this square, so that people again get the benefit of the corners (see also above 4:8).

מוציאין את המדה כנגדן – if these protrusions are near the northeastern corner, we see as if there is another protrusion corresponding to it on the southwestern corner, and a chord is stretched from one to the other and measures from the chord and outward, in order that the [Sabbath] limit is equivalent to the two corners, and it won’t be long here and short there.

ועושין אותן – the [Sabbath] limits square, so that there should be two-thousand [cubits] to the sides like there is in the middle. But not round, so that there will be two-thousand [cubits] in the middle, and on the sides, they are reduced in the manner of something round.

נותנים קרפף לעיר (for measuring the Sabbath limits, we allow an area of seventy-square cubits outside the town added to the town – for the purpose of the Sabbath limits) – all who come to measure the [Sabbath] limits leaves to the city/town the air-space of seventy cubits and left-overs, which are seventy cubits and two-thirds of a cubit, and from there, he begins to measure two-thousand cubits, as it states (Numbers 35:4): “[The town pasture that you are to assign to the Levites] shall extend a thousand cubits outside the town wall all around,” the Torah stated that one should give outside [the wall] and afterwards measure, meaning to say, give it an area of seventy-square cubits and remnants outside the town added to the town and afterwards measure from there and beyond/further.

Introduction A karpaf is a field used for storing wood. Its typical size is seventy cubits and a fraction long. In our mishnah the sages debate whether the size of a town is automatically extended by a karpaf.

לא אמרו קרפף אלא בין שתי עיירות – two towns that are adjacent/near each other, they given seventy cubits and left-overs to each one in order to attach/combine them through these enclosures to become like one city, and a person who comes to walk from one of them [through] its neighbor measures for himself two-thousand cubits from outside its neighbor, because since both of them are like one town/city through these enclosures that connect between them. And the Halakha is according to the Sages, for we don’t place an enclosure for one town/city, but rather only between two towns/cities.

They give a karpaf [as an extension] for every town, the words of Rabbi Meir. According to Rabbi Meir, when measuring the Shabbat limit they extend a karpaf’s length of a field to the size of the city. From the end of this field they will measure the 2000 cubits square.

But the sages say: they said [the of a] karpaf only in regard to two towns that if there was to this one [a piece] of land of seventy cubits and a fraction and to the other one [a piece of land] seventy cubits and a fraction, they can consider the karpaf as combining the two into one. The other sages do not agree that every city is automatically extended by a karpaf. They agree that there was a halakhah stated concerning a karpaf and its use in extending a city, but this halakhah is more limited in scope. If there are two cities close enough to one another that if there was a karpaf of seventy and a fraction cubits attached to each one, they would overlap (they are not more than 140 and 2/3 cubits apart), then the two cities can be considered one. The ramification would be that people could go from one to the other and that their Shabbat border would be drawn around the two cities.

וכן שלשה כפרים משולשים – on actually a triangle, but the third stands from afar corresponding to between the outer ones (i.e., towns) , and everything, for whereas, the middle [town] enters between them and there isn’t anything between this one and that one other than one-hundred and forty one and one-third cubits , which are seventy cubits and two-thirds [of a cubit] to this one, and seventy and two-thirds [of a cubit] to that one, and similarly, to the side of the other outer city/town. There is nothing between the middle one (i.e., town/city) and it other than one-hundred and forty-one cubits and one-third [of a cubit], all three of them (i.e., the towns/cities) are thought of as one [city/town]. But the person who leaves from one of them to to go through its neighbor counts from the wall of its outer neighbor. And how much should there be between the middle [city/town] to the outer [city/town]? Two-thousand cubits, for since the middle [town/city] is capable of going to the outer one and outer one to the middle one without an Eruv, we state that we see it as if the middle one is placed between them. But if it is further than two-thousand [cubits], we don’t say that we see it.

Introduction This mishnah deals with three villages in the shape of a triangle. If they are close enough to each other they can be treated as one village, and one eruv can be set for all three and the Shabbat border is drawn around all three.

So also three villages arranged in the shape of a triangle, if between the two outer ones there is a distance of a hundred and forty-one and a third cubits, the middle one causes all the three of them to be regarded as one. In the previous mishnah we learned that if there were less than 70 and a fraction cubits between two towns, that they can be treated as one town and that the Shabbat border is drawn around the two of them together. Here we learn that if there are three towns in the shape of a triangle, the middle town can join the outer one’s together, as long as there is not an empty space of more than 140 and a third cubits (twice 70 and a fraction) between each outer town and the middle, joining town. In other words, they are all treated as if they are in a row, a situation which we dealt with in the previous mishnah.

אין מודדין – two-thousand cubits of the Sabbath limit other than with a flax rope that is fifty cubits long.

Introduction This mishnah discusses how they actually go out and measure the Shabbat limit.

לא פחות – that if the rope is short, it is greatly stretched and lengthens [one must say, the measurement].

They measure the Shabbat limit only with a rope fifty cubits long, neither less nor more. The mishnah mandates the use of a fifty cubit rope in measuring the Shabbat limit. A shorter rope will stretch and yield to large of an area, whereas too long of a rope will not stretch enough the area will be too small.

ולא יותר – when it is too long, it becomes heavy, he doubles it at its middle and shortens it.

And one should measure only while holding the end of the rope on a level with his heart. Measuring with a rope requires two people, one to hold each end of the rope. If the two hold the rope in different places the measurement will be off. Therefore, the rabbis said that the rope should be held at the level of one’s heart.

אלא כנגד לבו (at level with his heart) – The Sages established for him a place to put the head of the rope, every person level with his heart, for if this person would place it corresponding to his neck and the other corresponding to his feet, the rope would shorten and the [Sabbath] limits would grow shorter.

If he was measuring and he reached a valley or a wall he spans it and resumes his measuring. If when measuring they come to a small valley (we might call this a large ditch) or a wall, the elevation of the wall or the descent into the ditch should not count as part of the measuring of the Shabbat limit. What they should do is span the rope over the valley, with one person standing on one side and the other person standing on the other. Similarly, if they get to a wall they do not run the rope over the wall, measuring the incline and decline leading up to the wall. Rather they measure up to the wall, then the thickness of the wall and then they proceed from the other side.

If he reached a hill he spans it and resumes his measuring, provided he does not go beyond the Shabbat limit. The same way they measure the wall and valley is how they measure a hill. However, in all of these cases they cannot go beyond the Shabbat limit. What this means is that if the valley, wall or hill were wide within the limit (too wide for a fifty cubit rope), but narrower outside the limit, they should not walk out of the Shabbat limit to perform their measurements and then set a place parallel to that point within the limit. The Talmud explains that the problem would be that if others saw them doing this, they might think that the point where they went to measure was the Shabbat limit, and not realize that they were measuring outside of the border in order to set up a parallel point within the border.

מבליעו (takes account only of the horizontal span/includes it) – if it is not fifty cubit wide from border to border from above, even though there is in its sloping going more than one-thousand, we don’t say that he should raise the measurement of his slope to the measurement of the [Sabbath] limit, but rather, this should stand on the border from here, and that should stand on its border from there and absorb (i.e., include) it from the slope with one rope.

If he is unable to span it in connection with this Rabbi Dostai ben Yannai stated in the name of Rabbi Meir: “I have heard that they pierce the hills.” The mishnah now deals with a valley or hill which were too big to measure with a fifty cubit rope, or were narrow only outside of the Shabbat limit. Rabbi Dostai says that we look at the mountains as if they were pierced. In other words, their ascent and descent are not taken into account. The Talmud explains how this is done. They use a small rope of four cubits, and the person holding below puts the rope next to his heart and the person holding above puts the rope next to his feet. In this way the four cubits are lessened a certain percentage for every four cubits. This is the size of the mountain’s ascent and descent, according to the rabbis. If you are having trouble picturing this, imagine a right triangle with its slope ascending, as if it was going up the mountain. If the top line is four cubits (the length of the rope) and the person hold the rope below is 3 cubits (the size of an average person), then you have a triangle whose sides are 4, 3 and 5, the side of 5 being the slope going up the hill (all of this is remembered from 10th grade geometry thank you Mr. Formica!). Thus the five cubits up the mountain are spanned with a four cubit rope, thereby gaining one cubit for every four. [I hope this helped!].

וחוזר למדתו – for since it teaches, “continues his measuring” – implying that if its width that corresponded to the town/city was more than fifty [cubits] and he was not able to absorb it/include it there with the rope, and with one of its heads that does not correspond to the town/city, he can absorb it/include it there, and measure and go there from the border and beyond until it corresponds to the place where the the width of the valley ends sin it corresponding to he city/town, and he returns to his measurement corresponding to the town/city and completes the measurement of its [Sabbath] limits.

הגיע להר מבליעו – and this is so that the mountain/hill will not be standing upright a great deal, but rather slanting, for in the walking of five cubits from it, he will not raise it (i.e., the rope) other than ten handbreadths, if it is standing straight up until with at least of the distance of five cubits it is standing upright ten handbreadths, he doesn’t include it/absorb it, but rather, estimates it alone and goes on.

והוא שלא יצא חוץ לתחום – when he measurer goes to include the hill/mountain or the valley, he should not leave outside of the [Sabbath] limit to a a place where the tops of the valley are short – that he is able to absorb them there in order that he can return afterwards to his measurement corresponding to the town/city, as a decree, because a person who sees it measures it and goes there would say that the measurement of the [Sabbath] limit of the sides of the city/town come up to here.

בזו אמר רבי דוסתאי – with this, to exclude the city of refuge and the heifer whose neck is broken that is nearest to the space/cavity that they don’t estimate the level distance between two places separated by mountains (see Talmud Eruvin 58a-b – because they are from the Written Torah).

מקדרין – they perforate, they see as if they perforate them and measure the path of the perforation, to exclude the measurement of its sloping, as we stated in the Gemara (Tractate Eruvin 58b) that they measure it with a rope of four cubits and the bottom they place the rope corresponding to his heart and at the top corresponding to his feet, and similarly they measure it all four cubits by four cubits and they deduct the slope of all four cubits by half the height of a person. And the Halakha is according to Rabbi Dostai.

אין מודדין אלא מן המומחה – a person who is a specialist in measuring, and the Gaon explained that the word מומחה is the language from (Numbers 34:11): “and abut on the eastern [slopes] of the Sea of Chinnereth/Kinneret,” meaning to say that they intent to measure the bottom ab initio from the place that is level and straight, in order that they would not need to perforate.

Introduction This mishnah continues to deal with measuring the Shabbat limit.

ריבה למקום אחד ומיעט למקום אחר – that they found signs of this [Sabbath] limit long and protruding corresponding to the signs of the [Sabbath] limit in the corner that is opposite it.

They measure [the Shabbat limit] only through an expert. The Shabbat limit should be measured only by an expert at taking such measurements. As we saw in yesterday’s mishnah, taking such measurements was not easy, so it is understandable why the rabbis required this to be done by an expert.

שומעין למקום שריבה – and we remove the shorter measurement, that is corresponding it, because it did not initially stretch the rope all the way. And it is taught in the Tosefta [Eruvin 4:`6 – in the Lieberman edition – but it is in chapter 6 according to the Erfurt manuscript] that he must stretch it with all of his strength [and measure].

If he extended the limit at one point and limited it at another, they observe the place where he extended it. There are several different explanations for this section. The Rambam, basing himself on the Talmud, explains that this refers to an expert who measured the limit and it was longer than the people of the city thought at one point, but shorter at another point. The mishnah teaches that just as the people of the city must listen to the expert’s measurement for where he limited the size, so too they may listen to him with regard to the place where he expanded it. Others explain that on one side he came up with two different measurements. For instance, his measurement to the northeast was longer than that to the southeast. In such a situation we assume that the shorter measurement was mistaken and we listen to the longer one.

ריבה לאחד ומיעט לאחר – this is what he said: if there was a greater distance for one [expert] and a lesser distance for the other [expert], for the two people who measured were experts – this one had a greater distance and the other a lesser distance.

If there was one who made it a greater distance and one who made it a lesser distance, the greater distance is observed. If two experts come up with different measurements, the bigger measurement is observed.

Even a slave and even a female slave are believed when they say, “Thus far is the Shabbat limit”, since the sages did not enact the law in order to be strict but in order to be lenient. Anybody is trustworthy to testify concerning where the Shabbat limit is, even slaves and female slaves who normally cannot testify. In Ketuboth 2:10 we also learned that the rabbis allowed minors to testify where the Shabbat border was, or more precisely they allow a person who has reached majority age to testify where the Shabbat border was when they were a minor. The mishnah explains that the rules concerning the Shabbat limit were meant to create leniencies, to allow people to travel further, and not to be stringent. This is because going past the Shabbat limit is only a rabbinic prohibition (derabanan), and therefore in cases of doubt, the halakhah can be lenient.

עיר של יחיד – as, for example that one person acquired it all and he rents out all of its houses to the people that are living there, and afterwards, it becomes the property of many.

Introduction This mishnah does not seem to have anything to do with our chapter. The previous mishnayot discussed measuring the city in order to determine the Shabbat border. The topic is therefore “eruvei techumin” Shabbat border eruvin which allow one to travel an added 2000 cubits outside of the city. The remainder of the chapter will also deal with this subject. This mishnah, in contrast, deals with “eruvei hatzerot” courtyard eruvin, or “shitufei mevuoth” alley partnerships, which allow people to carry within the city on Shabbat. Traditional commentators struggled to understand what this mishnah is doing here and offered various solutions. Abraham Goldberg, in his modern commentary to Mishnah Eruvin, suggests that there is a certain affinity in language between this mishnah and the preceding mishnayot, but his suggestion is also not without its difficulties. In any case, the mishnah deals with an eruv/shittuf (partnership) that allows one to carry within a city. A city that has a wall ten handbreadths high, and a gate that is locked at night, is treated like an alley, and hence if there is an “alley partnership” meaning a shared meal (which for convenience sake I will call “an eruv” people can carry within the entire city. However, there is a difference in this matter between a privately owned city where an individual owns the city and rents out houses to others, and a city owned by many of its residents. In a privately owned city, they may set up an eruv and everyone may carry in the entire city. However, in a publicly owned city, they must leave one area that does not participate in the eruv. This is done so that people don’t forget that it is forbidden to carry in the public domain without an eruv. The area that does not participate in the city’s eruv may set up its own eruv for its own area, and carry within that area, but not throughout the rest of the city. The mishnah deals with a city owned by an individual that becomes a publicly owned city and vice versa. Similarly it deals with the size of the area that cannot participate in a publicly owned city eruv.

מערבין את כולה – in the manner that they create a symbolic community of residence (i.e., an Eruv) when it belonged to a single individual that didn’t require a remnant.

If a town that belonged to an individual was converted into one belonging to the many, they may make an eruv for the entire town. As we explained above, for a town owned by an individual they may set up an eruv that allows all of the town’s residents to carry within the entire town. Our mishnah teaches that even if this town is converted into one owned by the many, they still may set up an eruv for the entire town. Its conversion does not affect its status.

אין מערבין את כולה – for it is forbidden to make an Eruv for a city/town belonging to many if he doesn’t leave known houses without an Eruv, for this remnant is a recognition that the reason is because of an Eruv, so that it would not forget the laws of the public domain. And this is the case, since it [belonged] to the group, and required a remnant even though that now it would be judged as that of an individual as at first.

But if a town belonged to the many and was converted into one belonging to an individual, they may not make an eruv for the entire town unless they excluded from it a section the size of the town of Hadashah in Judea, which contains fifty residents, the words of Rabbi Judah. Rabbi Shimon says: three courtyards each of which contains two houses. Similarly, a town which used to belong to the many and now is acquired by an individual is still treated as a town which belongs to the many. Its status is also not affected by its conversion. Therefore, they may not set up an eruv to allow people to carry in the entire town. Rather they must exclude from the area which participates in the eruv a section the size of the town Hadashah in Judea. “Hadashah” means new, and is mentioned in Joshua 15:37. Here the name of the city is read “midrashically” it is a new city which adds to the old city, sort of an appendage to the older city. In this “New City”, there were 50 residents. According to Rabbi Judah, by excluding an area this size, they may set up an eruv in the rest of the city. Rabbi Shimon disagrees and holds that the excluded part need only be an area the size of three courtyards, each of which has at least two homes. This would probably yield an area slightly smaller than that according to Rabbi Judah’s ruling.

אלא אם כן עשה חוצה לה – a remnant that was not made into a symbolic community of residence with the rest of the city/town, but it something remarkable that comes to teach us that even a remnant of something outside it has an effect on the rest of the city/town.

כעיר חדשה שביהודה – there was a city in Judah and its name was Hadasha, and there not there other than two temporary residents/inhabitants , and this is the smallest city/town that is in all of land of Judea and it was the remnant to a larger city that is adjacent to it, and this is measurement of the remnant that one needs to leave over in a city/own that they did not make into a symbolic community of residence (i.e., Eruv) with the others because of recognition.

רבי שמעון אומר שלש חצירות כו' – and the Halakhic decision is that even one house in one courtyard is a remnant. But a city that doesn’t have other than only one opening even if was of many [people], there is no need for remnant.

מי שהיה במזרח – in the field, and he sanctified for himself the [Sabbath] day and he was far from his Eruv more than two-thousand [cubits], for his Eruv is not an Eruv, since he is not able to walk and to carry, it would be for him a Sabbath camp in his house when his Eruv is not an Eruv.

Introduction This mishnah returns to the subject of Shabbat border eruvin.

If one was in the east and said to his son, “Prepare for me an eruv in the west”, or if he was in the west and he said to his son, “Prepare for me an eruv in the east”, if the distance between him and his house was no more than two thousand cubits and that between him and his eruv was more than this, he is permitted to go to his house but forbidden to go to his eruv. If the distance to his eruv was no more than two thousand cubits and that to his house more than this, he is forbidden to go to his house but permitted to go to his eruv. Before this person left his home on Friday, he told his son to set up for him an eruv to either the west or east of the city. At dusk on Friday eve, he finds himself on the opposite side of the city. If he is two thousand cubits or less from his home but more than two thousand cubits from his eruv, he may go to his home but not to his eruv. In other words, his eruv is ineffective and he may not go two thousand cubits beyond it. Since when Shabbat began he could not reach his eruv, which was more than two thousand cubits away from him, we say that his intention was that his home would be his “Shabbat place” and from his home, and not the eruv, we measure a Shabbat limit of 2000 cubits. If, on the other hand, he is 2000 cubits or less from his eruv but more than that from his home, he may go to his eruv but not to his home. Again, since he couldn’t get to his home when Shabbat began, we assume that he wished that his eruv would be his “Shabbat place” and from that point and that point only he can travel 2000 cubits.

בעיבורה של עיר (within the outskirts of the city) – in one of the houses that stands within seventy cubits and left-overs.

One who puts his eruv within the extension of a town, he has done nothing. If a person puts his eruv within the extensions of the city, his eruv doesn’t help him at all. Even without the eruv, he can go 2000 cubits beyond the extensions of the city. Rather an eruv should ideally be put 2000 cubits beyond the city and its extensions. In this way it extends the distance a person can travel in that direction. The “extensions of the city” refer to the inns and shops which are outside of the city but count in measuring the city’s borders.

לא עשה ולא כלום – for without an Eruv also, he has from the city/town two-thousand cubits in every direction, and the entire city/town with its outskirts are considered to him as four cubits.

If he put it even one cubit only beyond the limit he loses what he gains. This refers to a person who sets up his eruv outside the city, but within the 2000 cubit border which surrounds it. This is where an eruv should be set up. The mishnah teaches that every cubit he gains in his ability to travel on one side of the town, he loses on the other. So if he puts the eruv 1000 cubits outside the town on the west, he may now travel 3000 cubits to the west but only 1000 cubits to the east.

נתנו חוץ לתחום – outside of the outskirts of the city/town. And this is explained in the Gemara (Tractate Eruvin 60b).

מה שנשכר –[what he gains] in this direction, he loses in the direction that is opposite it. For he counts from the Eruv two-thousand [cubits] in every direction if it and if he placed [something] at the end of one-thousand [cubits] to the east, it is found that the two-thousand [cubits] of the east end at the conclusion of three-thousand [cubits] of the city and he has gained one-thousand, but the two-thousand [cubits] of the west end at the end of one-thousand [cubits] of the west of the city, and he lost one-thousand [cubits]. And this comes to tell us that the city does not count in the total of the two-thousand [cubits] of the west but rather all of it is like four cubits. And these words [apply] when the two-thousand [cubits] do not end from the Eruv to the side of the city/town, but rather, at the end of the city/town or outside of it, but if they end in the middle or the city or at whatever place within it, he cannot walk within the city/town other than up to the point where the two-thousand cubits of the Eruv end, and not further, as it is taught nearby (in the next Mishnah).

אנשי איש גדולה – that they (i.e., the residents of a large town) had a small town within the two-thousand [cubits] and they depart from their city and count and walk the path of the small [city/town] that is adjacent/nearby, they walk through all of the small town/city that is adjacent to them like four cubits and complete their measurement outside of it.

The people of a large town may walk through the whole of a small town, but the people of a small town may not walk through the whole of a large town.
How is this so? If a man was in a large town and deposited his eruv in a small town or if he stayed in a small town and deposited his eruv in a large town, he may walk through all the town and two thousand cubits beyond it.
Rabbi Akiva says: he only has the place of his eruv and another two thousand cubits.
The wording of our mishnah is somewhat difficult, and the talmudic sages already recognized different versions. However, the different versions are usually explained the same way. All agree that one who resides in a town and begins Shabbat there can travel two thousand cubits in all directions. However, the sages debate concerning a person who resides in one town but puts his eruv in another town. The question is: does this eruv, placed in another town, allow him to walk throughout the town and two thousand cubits around it, or is the area of the town included in the two thousand cubits? In other words, since he acquired his “Shabbat place” in that town through an eruv and not through his actually being there, is he treated as if he was there or do we look at this as a normal case of placing one’s eruv outside of one’s own town?
The other issue in the mishnah is concerning one who measures the two thousand cubits around his city and finds that another city is within this area. If the two thousand cubits ends in the middle of the city, all of the sages agree that he cannot go anywhere beyond the city on the other side. However, if the two thousand cubits ends at the end of the city, the city is treated as if it was merely four cubits in area and it doesn’t count for the two thousand cubit measure. Rather the two thousand cubits is completed on the other side of the city. This halakhah is the first section of the mishnah.
Section one: As I explained in the introduction, the wording of this mishnah is quite difficult. I shall explain the mishnah in the same that Albeck and Kehati do. The people of a large town, who have a small town entirely within their 2000 cubit Shabbat border, may walk throughout the entire small town and it counts only as four cubits toward their Shabbat limit. The remaining 2000 cubits surrounding the large town continue on the other side. For instance if there are 96 cubits from the large town to the small town, and the small town is 1800 cubits, he may walk through the whole small town and another 1900 cubits on the other side, since the town itself counts as only four cubits.
However, if the Shabbat border of a small town ends within a neighboring large town, the people from the small town can only walk within it up until their border ends.
We should note that according to this explanation, the size of the person’s original town does not seem to matter all that much. All that matters is whether or not the Shabbat border ends within the neighboring town.
Section two: The phrase “how is this so” does not seem to explain the previous clause in the mishnah. Hence, the Yerushalmi removes the word, whereas the Bavli adds in an entire clause. In any case, it seems that this is a new section and not a continuation of the previous one. This section deals with a person from one city who puts his eruv in another city. According to the first opinion, if one puts his eruv in another city that is within the 2000 cubits of one’s own city, the eruv makes the person as if he was a full resident of that city. Therefore, he may walk the full area of the city, plus 2000 cubits around it, just as can the residents of that city.
Rabbi Akiva disagrees and holds that the eruv in the other city works as do all normal eruvin they allow one to walk 2000 cubits beyond the eruv. If the city in which the eruv was placed goes further, he may not walk in that area of the city.

ואין אנשי עיר קטנה מהלכין את הגדולה – [the large town/city] in its entirety like four cubits, because the measurement of the [Sabbath] limits ended in the middle of the large city/town, therefore, the large city/town is not considered for them like four cubits and they don’t go there, but rather only until the end of their [Sabbath] limits.

כיצד מי שהיה מעיר גדולה – Our Mishnah is deficient and should be read as follows: The people of a large town/city walk through the entire small town/city but the people of a small town/city do not walk through all of the large city/town; in what case are these words said? When he measures two-thousand cubits. But, a person who places his Eruv within the city/town, whether the people of a large town/city placed it in a small town/city or whether the people of a small town/city placed it in a small town/city, they walk all the city/town that the Eruv is placed in it like four cubits. How so? He who was from a large city/town and placed his Eruv in a small town/city etc.

ור' עקיבא – disputes on the first Tanna/teacher and holds that the Eruv does not make the city/town in which it is placed like four cubits, and we don’t count two-thousand cubits other than from the place of the Eruv. But the Halakha is not according to Rabbi Akiva.

אימתי בזמן שאין בה דיורים – that their partitions were torn down and are not fit for inhabitants, for if it were fit for residents, even though there are none in it now, inhabitants are not considered everything like four cubits, and even if it is large like Antioch.

Introduction This mishnah is a direct continuation of the second clause of yesterday’s mishnah. To remind ourselves, Rabbi Akiva and the Sages had a debate concerning a person in one city who places his eruv in another city which is within the Shabbat border of his own city. According to Rabbi Akiva, this is treated as a normal case he may go 2000 cubits from his eruv and no more. The Sages hold that the city itself only counts as four cubits and that he may continue to go beyond the city the distance which remains to him after traveling from the first city.

נמצא קל תוכה מעל גבה – for whereas the [Eruv] on top of the cave , if he placed there his Eruv, he does not have anything other than two-thousand cubits from the place of his Eruv, for on top of it is not fit for inhabitants, but inside , he walks throughout and outside of it two-thousand cubits.

Rabbi Akiva said to them: Do you not agree with me that one who puts his eruv in a cave may walk no further than two thousand cubits from the place of his eruv? One who puts his eruv in a cave outside of his city, may travel another 2000 cubits outside of the eruv, including the length of the cave. The cave does not count for just four cubits rather each cubit within it counts. Rabbi Akiva asks the sages why they agree concerning this halakhah but not concerning one who puts his eruv in a neighboring city. In other words, why in the case of the city does the entire city only count as four cubits, no matter how large it is?

ולמודד שאמרו – even though that the Sages dispute on Rabbi Akiva when placing his Eruv in the city/town to state that the entire city is to him like four cubits, they admit that someone who comes from the place of his Sabbath camp and his measurement of two-thousand cubits ended, even in a cave where there are inhabitants, that he doesn’t enter further from his measurement at all.

They replied: when is this true? Only where no people dwell in it, but where people dwell in it one may walk through the whole of it and two thousand cubits beyond it. The sages respond that the rule regarding one who puts his eruv in a cave is true only if no one lives in the cave. The situation regarding the city is different when he puts his eruv there he counts as one of its residents. Just as the city’s residents may travel anywhere in the city and not have it count toward their 2000 cubits, so too he may travel anywhere in the city and not have it count towards his 2000 cubits.

Thus [where an eruv is put] within [the cave] the law is more lenient than [where one is put] on top of it. This section is way of remembering the rule of the Sages in section two. If the eruv is put on top of a cave which is in a city, then the eruv is in the city and he may walk within the entire city and not have it count toward his 2000 cubits. However, if he puts the eruv in the cave below the city, the cave and certainly the city count toward his 2000 cubit limit. This means that the law is more lenient when the eruv is on top then when it is within.

And to the measurer, of whom they spoke, they give him a distance of two thousand cubits even if the end of his measure terminates within a cave. In this section the sages agree with Rabbi Akiva concerning one who measures his Shabbat border, that he gets only 2000 cubits, even if this measure ends in the middle of a cave. Even if there are residents in the cave, he still cannot go through to the end of the cave, because his original Shabbat limit ended before he got there. This matches what we learned in the beginning of yesterday’s mishnah, concerning a Shabbat border that ends within a neighboring city. In such a case, he may only go up to the end of his Shabbat border.