Leviticus 7:28-36

²⁸And the Lord spoke to Moses, saying:

²⁹Speak to the children of Israel, saying: He that offereth a victim of peace offerings to the Lord, let him offer therewith a sacrifice also, that is, the libations thereof.

³⁰He shall hold in his hands the fat of the victim, and the breast: and when he hath offered and consecrated both to the Lord, he shall deliver them to the priest,

³¹Who shall burn the fat upon the altar, but the breast shall be Aaron’s and his sons’.

³²The right shoulder also of the victims of peace offerings shall fall to the priest for firstfruits.

³³He among the sons of Aaron, that offereth the blood, and the fat, he shall have the right shoulder also for his portion.

³⁴For the breast that is elevated and the shoulder that is separated I have taken of the children of Israel, from off their victims of peace offerings, and have given them to Aaron the priest, and to his sons, by a law for ever, from all the people of Israel.

³⁵This is the anointing of Aaron and his sons, in the ceremonies of the Lord, in the day when Moses offered them, that they might do the office of priesthood,

³⁶And the things that the Lord commanded to be given them by the children of Israel, by a perpetual observance in their generations.