Numbers 4:22

18“Don’t cut off the tribe of the families of the Kohathites from among the Levites;

19but do this to them, that they may live, and not die, when they approach the most holy things: Aaron and his sons shall go in and appoint everyone to his service and to his burden;

20but they shall not go in to see the sanctuary even for a moment, lest they die.”

21The LORD spoke to Moses, saying,

22“Take a census of the sons of Gershon also, by their fathers’ houses, by their families;

23you shall count them from thirty years old and upward until fifty years old: all who enter in to wait on the service, to do the work in the Tent of Meeting.

24“This is the service of the families of the Gershonites, in serving and in bearing burdens:

25they shall carry the curtains of the tabernacle and the Tent of Meeting, its covering, the covering of sealskin that is on it, the screen for the door of the Tent of Meeting,

26the hangings of the court, the screen for the door of the gate of the court which is by the tabernacle and around the altar, their cords, and all the instruments of their service, and whatever shall be done with them. They shall serve in there.