Deuteronomy 18:3-5

3This shall be the priests’ fair allotment from the people who offer sacrifices, whether bull or sheep – they must give to the priest the shoulder, the jowls, and the stomach.

4You must give them the best of your grain, new wine, and olive oil, as well as the best of your wool when you shear your flocks.

5For the Lord your God has chosen them and their sons from all your tribes to stand and serve in his name permanently.