Numbers 18:5-7

CLV(i) 5 You will keep guard of the holy place and guard of the altar so that no more wrath shall come on the sons of Israel. 6 As for Me, behold, I have taken your brothers, the Levites, from the midst of the sons of Israel as a gift for you, given to Yahweh to serve in the service of the tent of appointment. 7 Yet you and your sons with you shall keep your priesthood as to every matter of the altar and to that inside the curtain. Thus you will serve in the service. As a gift am I giving your priesthood. Yet the alien who comes near shall be put to death.