Numbers 18:17-18

¹⁷But the firstling of a cow, or the firstling of a sheep, or the firstling of a goat, thou shalt not redeem; they are holy: thou shalt sprinkle their blood upon the altar, and shalt burn their fat for an offering made by fire, for a sweet savour unto the LORD.

¹⁸And the flesh of them shall be thine, as the wave breast and as the right shoulder are thine.