Numbers 18:2-4

2But also bring your relatives with you from the tribe of Levi, your ancestral tribe, so they may join you and assist you and your sons in front of the tent of the testimony.

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.