Numbers 4:23-26

23from thirty years old and upward until fifty years old shalt thou number them; all that enter in to wait upon the service, to do the work in the tent of meeting. 24This is the service of the families of the Gershonites, in serving and in bearing burdens: 25they shall bear the curtains of the tabernacle, and the tent of meeting, its covering, and the covering of sealskin that is above upon it, and the screen for the door of the tent of meeting, 26and the hangings of the court, and the screen for the door of the gate of the court, which is by the tabernacle and by the altar round about, and their cords, and all the instruments of their service, and whatsoever shall be done with them: therein shall they serve.