Numbers 18:3-5

3They shall attend to your needs and all the needs of the tabernacle; but they shall not come near the articles of the sanctuary and the altar, lest they die—they and you also.

4They shall be joined with you and attend to the needs of the tabernacle of meeting, for all the work of the tabernacle; but an outsider shall not come near you.

5And you shall attend to the duties of the sanctuary and the duties of the altar, that there may be no more wrath on the children of Israel.