Numbers 18:3-6

3But as the Levites go about all their assigned duties at the Tabernacle, they must be careful not to go near any of the sacred objects or the altar. If they do, both you and they will die.

4The Levites must join you in fulfilling their responsibilities for the care and maintenance of the Tabernacle, but no unauthorized person may assist you.

5“You yourselves must perform the sacred duties inside the sanctuary and at the altar. If you follow these instructions, the Lord’s anger will never again blaze against the people of Israel.

6I myself have chosen your fellow Levites from among the Israelites to be your special assistants. They are a gift to you, dedicated to the Lord for service in the Tabernacle.