Commentary for Bava Metzia 8:5
הַמּוֹכֵר זֵיתָיו לְעֵצִים, וְעָשׂוּ פָּחוֹת מֵרְבִיעִית לִסְאָה, הֲרֵי אֵלּוּ שֶׁל בַּעַל הַזֵּיתִים. עָשׂוּ רְבִיעִית לִסְאָה, זֶה אוֹמֵר זֵיתַי גִּדְּלוּ, וְזֶה אוֹמֵר אַרְצִי גִדְּלָה, יַחֲלֹקוּ. שָׁטַף נָהָר זֵיתָיו וּנְתָנָם לְתוֹךְ שְׂדֵה חֲבֵרוֹ, זֶה אוֹמֵר זֵיתַי גִּדְּלוּ, וְזֶה אוֹמֵר אַרְצִי גִדְּלָה, יַחֲלֹקוּ:
If one sold his olive trees [to be cut for] (fire-) wood [and he left them in the ground], and they produced less than a revi'ith to a sa'ah [i.e., inferior olives, a sa'ah of which does not produce a revi'ith of oil], they belong to the owner of the trees. [For people are not particular about less than a revi'ith. The "revi'ith" here is aside from his expenses in harvesting and pressing. Our Mishnah speaks of one who sells his olive trees without specifying when they are to be cut. But if he (the seller) told him to cut them immediately, even less than a revi'ith belongs to the owner of the land. And if he told him to cut it when he wished, even more than a revi'ith belongs to the owner of the trees.] If they produced a revi'ith to a sa'ah, and one said: "My trees produced it," and the other: "My land produced it," they divide. If a river flooded his olive trees and transplanted them in his neighbor's field, and this one said: "My trees produced it," and the other: "My land produced it," they divide. [The Gemara construes this as an instance of the river washing away the trees along with their surrounding earth clumps. Since they can grow through them, they are not subject to the laws of arlah (forbidden fruits of the first three years). The first three years, they divide. For even though the other's land produces it, still, if not for the earth clumps, he would not be able to eat of it because of arlah. But after three years, it all belongs to the owner of the land, for he can say to him: "If I myself had planted then, could I not eat after three years!"]
Bartenura on Mishnah Bava Metzia
English Explanation of Mishnah Bava Metzia
If a flood washed away a man’s olive trees and set them in the midst of his fellow’s field [where they bore fruit], and the one said, “It was my trees that produced it”, and the other said, “It was my land that produced it”, let them share the produce.
Mishnah five deals with a situation where one sold olive trees to another person to cut them down as firewood, but he did not sell the land. The issue is to whom do the olives belong: to the one who owns the trees or to the one who owns the land.
Mishnah six begins to discuss the laws of renting, a topic which will be discussed from now until the end of the tractate. The first topic of discussion is the renting of houses and specifically the laws of eviction.
The scenario in section one of our mishnah is that Reuven sold his olive trees to Shimon but did not sell him the land. The intent was for Shimon to cut down the trees and use them as firewood. However, before Shimon did so the olive trees bore some olives with which it was possible to make olive oil. If the olive oil was of a poor quality, in other words it came from olives that produced less than a quarter-log of oil per seah, then the owner of the trees can keep the oil. Since there is not much oil and it is of a low quality, we can safely assume that Reuven does not care about it and therefore Shimon may keep it. However, if the trees produce a better quality and higher quantity of olive oil there may be a dispute. Reuven may justly claim that the olives grew from his ground and Shimon may justly claim that they grew from his tree. In such a case they split the value of the olive oil.
The scenario in section two is different from that in section one but it has the same law. In this case Reuven’s trees were washed up in a flood and landed on Shimon’s property where they took root and bore fruit. Again, Reuven claims that his trees bore the fruit and Shimon that his land bore the fruit. Again, they split the value of the oil.