Numbers 18:6-9

⁶And I, behold, I have taken your brethren the Levites from among the children of Israel; for you they are given as a gift unto the LORD, to do the service of the tent of meeting.

⁷And thou and thy sons with thee shall keep your priesthood in everything that pertaineth to the altar, and to that within the veil; and ye shall serve; I give you the priesthood as a service of gift; and the common man that draweth nigh shall be put to death.'

⁸And the LORD spoke unto Aaron: 'And I, behold, I have given thee the charge of My heave-offerings; even of all the hallowed things of the children of Israel unto thee have I given them for a consecrated portion, and to thy sons, as a due for ever.

⁹This shall be thine of the most holy things, reserved from the fire: every offering of theirs, even every meal-offering of theirs, and every sin-offering of theirs, and every guilt-offering of theirs, which they may render unto Me, shall be most holy for thee and for thy sons.