Numbers 18:2-7

²And also thy brethren, the tribe of Levi, the tribe of thy father, bring thou near with thee, that they may be joined with thee, and minister unto thee; while thou and thy sons with thee shall be before the tabernacle of the testimony.

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.