Numbers 18:3-9

³And they shall keep thy charge, and the charge of all the tabernacle: only unto the vessels of the sanctuary and unto the altar shall they not come near, that they may not die, either they or you.

⁴And they shall be joined unto thee, and keep the charge of the tabernacle of the congregation, respecting all the service of the tabernacle: and a stranger shall not come nigh unto you.

⁵And ye shall keep the charge of the sanctuary, and the charge of the altar; that there be not any more wrath upon the children of Israel.

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

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

⁸And the Lord spoke unto Aaron, And I, behold, I give thee the charge of my heave-offerings; of all the hallowed things of the children of Israel, unto thee have I given them as an official portion, and to thy sons, as a fixed right for ever.

⁹This shall belong to thee of the most holy things, from the fire-offerings: every oblation of theirs, namely, every meat-offering of theirs, and every sin-offering of theirs, and every, trespass-offering of theirs, which they shall render unto me, shall, as most holy things, belong to thee and to thy sons.