Related על מעשרות 3:2

One who brought his workers out to the field -- he does not have the right to feed them unless he has [already] tithed, and they do not have the right to eat unless they have tithed (cf. Maasr. 3:2 "they may eat and be exempt"). But if the homeowner brought them out [to the field] and placed a generous amount [of food] in front of them, they do not need to tithe.