Related sur Démaï 5:15

One who wishes to separate Terumah, and Terumah of tithes, and challah at the same time (see Dem. 5:2) takes [an amount] suitable for [the amount of] Terumah or the Terumah of Challah. And how much is that? One twentieth. And he says, "One hundredth part of what is here, behold, that which is on this side shall be tithe, and the remainder of the tithe is next to it, and another one forty-eighth of of what is here, behold, that which is on this side is chullin, and the remainder is Terumah on the whole is Terumah. One hundred[th] [of the chullin] that is here, behold, that which is on this side is tithe and the remainder of the tithe is next to it. That which I made tithe is made Terumah of tithe on it and the remainder is challah. [The portion set aside for] second tithe is on the north or on the south." And he exchanges it for money. Rabbi Shimon forbids it with [respect to] Terumah of tithes, and permits it with challah (Dem. 5:3). What case does this refer to? When everyone separates [tithes], he takes [a single joint portion of] challah from everyone, but when a few separate and a few do not separate, he takes challah from each and every one.

Workers that were sitting and eating, and they left over slices [of bread], and similarly with guests that were reclining and eating and they left over slices [of bread], and they gave them to the attendant, or there were others (i.e., poor people) who were collecting [the fallen slices] under them (i.e., under where the guests had been sitting), [the attendant] tithes from each and every one. [If someone] took the bread and made [it into] crumbs, or figs and made them into fig cakes, he tithes from one on everything, said Rabbi Yehudah. What case does this refer to? In a year of satisfaction (i.e., when there is enough to go around, see Minchat Bikkurim here), but in the other years he tithes each and every one.

One who purchases from a poor person, and so too a poor person to whom they gave slices of bread or figs, he takes tithes from each and every one. With [respect to] dates grown in the valleys (Bikkurim 1:10), he tithes from one on behalf of everything. In other places [where the dates are of lower quality], he takes tithes from each and every one. With [respect to] figs in years of satisfaction (see above) he takes tithes from one on behalf of everything, but in the other years he tithes each and every one.

One who purchases from a merchant tithes from each and every [bread] mold (see Menachot 94a:11), and if [the merchant] was bringing [vegetables from various farmers] and gathering them before [the purchaser], he takes tithes from each and every cucumber and from each and every bunch [of vegetables], and from each and every date. One who purchases from a shopkeeper, and goes back and takes from him a second time, even though he recognizes the barrel [of wine], he may not tithe from this [purchase] on behalf of that [prior purchase (see Dem. 5:6)].

One who purchases from a merchant tithes from each and every [bread] mold (see Menachot 94a:11), and if [the merchant] was bringing [vegetables from various farmers] and gathering them before [the purchaser], he takes tithes from each and every cucumber and from each and every bunch [of vegetables], and from each and every date. One who purchases from a shopkeeper, and goes back and takes from him a second time, even though he recognizes the barrel [of wine], he may not tithe from this [purchase] on behalf of that [prior purchase (see Dem. 5:6)].