Exodus 29:27-28

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.