Numbers 18:2-4

2Bring the other Levites from your ancestor’s tribe to join you and help you and your sons serve in front of the tent of the words of my promise.

3They will work for you, doing whatever work is necessary for the whole tent. But they must not come near the altar or the furnishings in the holy place, or they will die, and you will die, too.

4They will join you and do whatever work is necessary for the tent of meeting, including all the maintenance work for the tent. But no one else may come near you.