Numbers 18:17-18

17But 1the firstborn of an ox, the firstborn of a sheep, or the firstborn of a goat, you shall not redeem; they are holy. 2You shall sprinkle their blood on the altar and offer up their fat in smoke as an offering by fire, for a soothing aroma to the Lord.

18However, their 3meat shall be yours; it shall be yours like the 4breast of a wave offering and like the right thigh.