Numbers 18:17-19

17You must not pay for the firstborn of a cow, a sheep or a goat. Those animals are holy. Splash the blood from those animals on the altar and burn the fat from them. The smell will make the Lord happy.

18And the meat of those animals belongs to you. In the same way, the meat of the ribs and the right back leg of the special gifts that you lift up to me also belong to you.

19I have given all the gifts that the Israelites offer to the Lord to you, your sons and your daughters. That is a rule for all time. That is the Lord's special promise to you and to your descendants for all time.’