Numbers 18:1-4

GOD said to Aaron, “You and your sons, along with your father’s family, are responsible for taking care of sins having to do with the Sanctuary; you and your sons are also responsible for sins involving the priesthood. So enlist your brothers of the tribe of Levi to join you and assist you and your sons in your duties in the Tent of Testimony. They will report to you as they go about their duties related to the Tent, but they must not have anything to do with the holy things of the Altar under penalty of death—both they and you will die! They are to work with you in taking care of the Tent of Meeting, whatever work is involved in the Tent. Outsiders are not allowed to help you.