Numbers 18:17-19

“But you must not redeem the firstborn of a cow, a sheep or a goat; they are holy. Splash their blood against the altar and burn their fat as a food offering, an aroma pleasing to the LORD. Their meat is to be yours, just as the breast of the wave offering and the right thigh are yours. Whatever is set aside from the holy offerings the Israelites present to the LORD I give to you and your sons and daughters as your perpetual share. It is an everlasting covenant of salt before the LORD for both you and your offspring.”