Exodus 29:26-28

26Then take the breast of Aaron’s ordination ram, and lift it up in the Lord’s presence as a special offering to him. Then keep it as your own portion.

27“Set aside the portions of the ordination ram that belong to Aaron and his sons. This includes the breast and the thigh that were lifted up before the Lord as a special offering.

28In the future, whenever the people of Israel lift up a peace offering, a portion of it must be set aside for Aaron and his descendants. This is their permanent right, and it is a sacred offering from the Israelites to the Lord.