Terumos 9:2-3

Terumos 9:2

If a person planted terumah, what grows is liable to the various gifts to the needy. Both kohanim and non-kohanim may gather these. Since the non-kohanim cannot eat the produce of terumah, they must sell what they collect to kohanim at the price of terumah; they can use the money however they wish. Rabbi Tarfon says that only needy kohanim may collect it because a non-kohein might absent-mindedly put some of this produce in his mouth. Rabbi Akiva disagrees; he says if that’s so, then we should only allow ritually-clean people to collect such produce.

Terumos 9:3

If a person planted terumah, what grows is liable to tithes and the tithe for the needy. Both kohanim and non-kohanim may gather it but, since the non-kohanim cannot eat it, they must sell what they collect to kohanim at the price of terumah, using the proceeds as they wish. It is praiseworthy to thresh this produce by flailing it rather than by having animals tread it (as this removes the problems raised by the animals eating it). If one does thresh with an animal, he must hang a basket around the animal’s neck containing some of the same type of produce. In this way, he neither muzzles the animal (which is forbidden when the animal is treading grain) nor feeds it terumah.