Numbers 18:16-18

New Revised Standard Version, Anglicised Catholic Edition

¹⁶ Their redemption price, reckoned from one month of age, you shall fix at five shekels of silver, according to the shekel of the sanctuary (that is, twenty gerahs). ¹⁷ But the firstborn of a cow, or the firstborn of a sheep, or the firstborn of a goat, you shall not redeem; they are holy. You shall dash their blood on the altar, and shall turn their fat into smoke as an offering by fire for a pleasing odour to the Lord; ¹⁸ but their flesh shall be yours, just as the breast that is elevated and as the right thigh are yours.