Numbers 18:15-18

15The first offspring of the womb from all flesh, whether human or animal, offered to Adonai, is yours. However, you are to redeem the firstborn of man and the firstborn of unclean animals.

16When they are a month old, you are to redeem them at the redemption price of five shekels of silver by the Sanctuary shekel, or 20 gerahs.

17But the firstborn of the ox, sheep or goat you are not to redeem. They are holy. You are to sprinkle their blood on the altar, and their fat you are to burn as a fire offering, a pleasing aroma to Adonai.

18Their meat—the breast of the wave offering and the right thigh—is yours.