Numbers 18:3-9

³And they shall keep thy charges, and the charges of the tabernacle; only they shall not approach the holy vessels and the altar, so both they and you shall not die.

⁴And they shall be joined to thee, and shall keep the charges of the tabernacle of witness, in all the services of the tabernacle; and a stranger shall not approach to thee.

⁵And ye shall keep the charges of the holy things, and the charges of the altar, and so there shall not be anger among the children of Israel.

⁶And I have taken your brethren the Levites out of the midst of the children of Israel, a present given to the Lord, to minister in the services of the tabernacle of witness.

⁷And thou and thy sons after thee shall keep up your priestly ministration, according to the whole manner of the altar, and that which is within the veil; and ye shall minister in the services as the office of your priesthood; and the stranger that comes near shall die.

⁸And the Lord said to Aaron, And, behold, I have given you the charge of the firstfruits of all things consecrated to me by the children of Israel; and I have given them to thee as an honor, and to thy sons after thee for a perpetual ordinance.

⁹And let this be to you from all the holy things that are consecrated to me, even the burnt offerings, from all their gifts, and from all their sacrifices, and from every trespass offering of theirs, and from all their sin offerings, whatever things they give to me of all their holy things, they shall be thine and thy sons’.