Numbers 18:7-8

7And thou and thy sons with thee shall keep your priesthood for everything of the altar, and for that within the veil; and ye shall serve: I give you the priesthood as a service of gift: and the stranger that cometh nigh shall be put to death.

8And Jehovah spake unto Aaron, And I, behold, I have given thee the charge of my heave-offerings, even all the hallowed things of the children of Israel; unto thee have I given them by reason of the anointing, and to thy sons, as a portion for ever.