Numbers 4:23-27

from thirty years old and upward to fifty years old you shall count them: all who can enter to perform service, to do the work in the tent of meeting.

This is the service of the families of the Gershonites, in serving and in carrying:

they shall carry the curtains of the tabernacle and the tent of meeting with its covering and the covering of fine leather that is on top of it, and the curtain for the entrance of the tent of meeting,

and the curtains of the courtyard, the curtain for the entrance of the gate of the courtyard that is around the tabernacle and the altar, and their ropes and all the equipment for their service; and everything that is to be done by them, they shall perform.

All the service of the sons of the Gershonites, that is, all their loads and all their work, shall be performed at the command of Aaron and his sons; and you shall assign to them as a duty all their loads.