Numbers 4:19

4:19 but in order that they will live and not die when they approach the most holy things, do this for them: Aaron and his sons will go in and appoint each man to his service and his responsibility.

Numbers 8:22

8:22 After this, the Levites went in to do their work in the tent of meeting before Aaron and before his sons. As the Lord had commanded Moses concerning the Levites, so they did.

Numbers 18:2

18:2 “Bring with you your brothers, the tribe of Levi, the tribe of your father, so that they may join with you and minister to you while you and your sons with you are before the tent of the testimony.

Numbers 27:3

27:3 “Our father died in the wilderness, although he was not part of the company of those that gathered themselves together against the Lord in the company of Korah; but he died for his own sin, and he had no sons.