Numbers 4:12

4:12 Then they must take all the utensils of the service, with which they serve in the sanctuary, put them in a blue cloth, cover them with a covering of fine leather, and put them on a carrying beam.

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.