Numbers 18:2-7

2But also bring your brothers with you, the tribe of Levi, the tribe of your father, so that they may 1join you and serve you, while you and your sons with you are before the tent of the testimony. 3And they shall perform duties for you and the duties of the whole tent, but 2they shall not come near the furnishings of the sanctuary and 3the altar, or both they and you will die. 4They shall join you and perform the duties of the tent of meeting, for all the service of the tent; but 4an unauthorized person shall not come near you. 5So you shall perform the 5duties of the sanctuary and the duties of the altar, 6so that there will no longer be wrath on the sons of Israel. 6Behold, I Myself 7have taken your 8fellow Levites from among the sons of Israel; they are 9a gift to you, 10dedicated to the Lord, to perform the service for the tent of meeting. 7But you and your sons with you shall 11attend to your priesthood for everything that concerns the altar and inside the veil, and you are to perform service. I am giving you the priesthood as 12a 13service that is a gift, and 14the 15unauthorized person who comes near shall be put to death.”