Numbers 18:6-8

King James Version

⁶ And I, behold, I have taken your brethren the Levites from among the children of Israel: to you they are given as a gift for the Lord, to do the service of the tabernacle of the congregation.

⁷ Therefore thou and thy sons with thee shall keep your priest's office for everything of the altar, and within the vail; and ye shall serve: I have given your priest's office unto you as a service of gift: and the stranger that cometh nigh shall be put to death.

⁸ And the Lord spake unto Aaron, Behold, I also have given thee the charge of mine heave offerings of all the hallowed things of the children of Israel; unto thee have I given them by reason of the anointing, and to thy sons, by an ordinance for ever.