Numbers 4:23

20 But they themselves are not to go in to see the holy place, even for a minute, for fear of death.

21 And the Lord said to Moses,

22 Let the sons of Gershon be numbered by families, in the order of their fathers' houses;

23 All those from thirty to fifty years old who are able to do the work of the Tent of meeting.

24 This is to be the work of the Gershonites, the things they are to do and take up.

25 They are to take up the curtains of the House, and the Tent of meeting with its cover and the leather cover over it, and the hangings for the door of the Tent of meeting;

26 And the hangings for the open space round the House and the altar, and the curtain for its doorway, with the cords and all the things used for them; whatever is necessary for these, they are to do.