Numbers 18:3-6

3They are to perform duties for you and for the whole tent. They must not come near the sanctuary equipment or the altar; otherwise, both they and you will die.

4They are to join you and guard the tent of meeting, doing all the work at the tent, but no unauthorized person may come near you.

5“You are to guard the sanctuary and the altar so that wrath may not fall on the Israelites again.

6Look, I have selected your fellow Levites from the Israelites as a gift for you, assigned by the Lord to work at the tent of meeting.