Leviticus 7:33-34

³³He that of Aaron’s sons offereth the blood, and the inner fatness, shall have also the right shoulder in his portion. (Yea, the priest, of the sons of Aaron, who offereth the blood, and the inner fat, shall also have the right shoulder for his portion.)

³⁴For I have taken from the sons of Israel the breast of raising, and the shoulder of separating, of their peaceable sacrifices, and I have given those to Aaron the priest and to his sons, by everlasting law, of all the people of Israel. (For I have taken from the Israelites the breast of raising, as a special gift, and the shoulder of separating, as a special contribution, out of their peace offerings, and I have given them to Aaron the priest, and to his sons, by an everlasting law, from all the people of Israel.)