פירוש על דמאי 2:4

הנחתומים – a baker who observes certain religious customs regarding tithes (i.e., he is a חבר) who purchased grain from aa person who does not observe certain religious customs regarding tithes (i.e., an עם הארץ ) which is doubtfully tithed produce, the Sages did not obligate him to separate [tithes].

Introduction Our mishnah deals with how various food professionals observe the laws of demai.

אלא כדי תרומת מעשר – [the heave-offering of the tithe that the Levite gives to the Kohen] which is one out of one-hundred (i.e., 1/100) but not Second Tithe (In years 1,2,4 and 5 of the seven-year cycle which is eaten in Jerusalem), because the officers of the king and his taskmasters beat them in every hour and say to them: see them cheaply, the Sages did not force them to give the Second Tithe for its trouble is great for one needs to consume it I Jerusalem. And especially when one sells it to a person who observes certain religious customs regarding tithes, for the person who acquires it separates out the Second Tithe, but if he sells it to someone who does not observe certain religious customs regarding tithes, he is liable to separate out the Second Tithe before he sells it.

Bakers the sages did not obligate them to separate [from demai produce] any more than suffices for terumat maaser and for hallah. The rabbis were lenient in mandating bakers to separate all of the tithes from demai (produce they bought from an am haaretz) because bakers barely make a profit. If the sages had been strict, bakers might have been left with a choice: go out of business or ignore rabbinic law. The baker did have to remove terumat maaser (the terumah taken from the tithe) and the hallah. These are of a higher level of holiness, but are not necessarily a large amount of produce. However, the baker did not have to take out second tithe.

החנונים – [the storekeepers] who sell a little bit at a time in the store, are not permitted to sell that which is doubtfully tithed, for since they profit a great deal on them, it is upon them to make things legally fit for use by giving the priestly dues. Alternatively, because they regularly sell to young children so that the young children will not eat that which is not legally fit for use by giving the priestly dues.

Grocers may not sell demai [produce]. Grocers, on the other hand, cannot sell demai until all the tithes, meaning terumat maaser, hallah and second tithe, have been separated. Evidently grocers made a greater profit than did bakers and hence the rabbis were more stringent with them.

כל המשפיעים (all wholesale dealers) – who sell with great abundance together.

All [merchants] who supply in large quantities may sell demai. Who are those who supply in large quantities? Those such as wholesalers and grain-sellers. Anybody who sells in large quantities is allowed to sell demai, under the assumption that he is providing a little extra so that the buyer can separate the tithes himself. The mishnah enumerates two types of merchants who usually sell in large quantities: wholesalers and grain merchants. In contrast, a grocer, referred to in section two, sells in more precise measurements and hence has to separate the tithes himself.

במדה גסה – further on it explains what is a selling in bulk.

רשאין למכור את הדמאי – it is the manner of man sellers together to increase on the measure and for that reason, they were called wholesale dealers who make an overflowing measure and add to the measures, and because of this they did not place upon them to separate out [tithes] on the doubtfully tithed produce other than for someone who purchases from them.

סיטונות (wholesale provision merchants) – they are the large business men who purchase grain from those who own it and sell it to storekeepers in a large measure/bulk.