Numbers 18:15-20

15The firstborn of every living thing, human or animal, presented to the Lord belongs to you. But you must certainly redeem a human firstborn, and redeem the firstborn of an unclean animal.

16You will pay the redemption price for a month-old male according to your assessment: five shekels of silver by the standard sanctuary shekel, which is twenty gerahs.

17“However, you must not redeem the firstborn of an ox, a sheep, or a goat; they are holy. You are to splatter their blood on the altar and burn their fat as a food offering for a pleasing aroma to the Lord.

18But their meat belongs to you. It belongs to you like the breast of the presentation offering and the right thigh.

19“I give to you and to your sons and daughters all the holy contributions that the Israelites present to the Lord as a permanent statute. It is a permanent covenant of salt before the Lord for you as well as your offspring.”

20The Lord told Aaron, “You will not have an inheritance in their land; there will be no portion among them for you. I am your portion and your inheritance among the Israelites.