Deuteronomy 18:3–5

3 And this shall be the priests’ due from the people, from those offering a sacrifice, whether an ox or a sheep: pthey shall give to the priest the shoulder and the two cheeks and the stomach. 4 qThe firstfruits of your grain, of your wine and of your oil, and the first fleece of your sheep, you shall give him. 5 For the Lord your God has chosen him out of all your tribes rto stand and minister in the name of the Lord, him and his sons for all time.