Numbers 18:15-20

15The firstborn of every womb, whether man or beast, that is offered to the LORD belongs to you. But you must surely redeem every firstborn son and every firstborn male of unclean animals. 16You are to pay the redemption price for a month-old male according to your valuation: five shekels of silver,1 according to the sanctuary shekel, which is twenty gerahs.2

17But 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, a pleasing aroma to the LORD. 18And their meat belongs to you, just as the breast and right thigh of the wave offering belong to you.

19All the holy offerings that the Israelites present to the LORD I give to you and to your sons and daughters as a permanent statute. It is a permanent covenant of salt3 before the LORD for you and your offspring.”

20Then the LORD said to Aaron, “You will have no inheritance in their land, nor will you have any portion among them. I am your portion and your inheritance among the Israelites.