Numbers 18:17-18

¹⁷But the firstling of a cow and of a sheep and of a goat thou shalt not cause to be redeemed, because they are sanctified to the Lord. Their blood only thou shalt pour upon the altar, and their fat thou shalt burn for a most sweet odour to the Lord.

¹⁸But the flesh shall fall to thy use, as the consecrated breast, and the right shoulder shall be thine.