Numbers 4:15-25

15 And when Aaron and his sons have made an end of covering the sanctuary and all the vessels of the sanctuary when the camp is to set forward, after that, the sons of Kohath shall come to bear it, but they shall not touch any holy thing, lest they die. These things are the burden of the sons of Kohath in the tabernacle of the testimony.
16 But unto the care of Eleazar, the son of Aaron the priest, shall be the oil of the light and the aromatic incense and the daily present and the anointing oil and the care of all the tabernacle and of all that is therein, in the sanctuary, and in the vessels thereof.
17 And the LORD spoke unto Moses and unto Aaron, saying,
18 Ye shall not cut off the tribe of the families of Kohath from among the Levites,
19 but thus do unto them that they may live, and not die, when they approach unto the holy of holies: Aaron and his sons shall come and place each one of them in his ministry and to his burden.
20 They shall not go in to see when the holy things are covered, lest they die.
21 And the LORD spoke unto Moses, saying,
22 Take also the sum of the sons of Gershon, throughout the houses of their fathers, by their families;
23 from thirty years old and upward until fifty years old shalt thou number them, all that enter in to the host to do work in the tabernacle of the testimony.
24 This shall be the service of the families of Gershon, to minister and to bear burdens:
25 They shall bear the curtains of the tabernacle and the tabernacle of the testimony, its covering, and the covering of badgers’ skins that is over it above and the hanging for the door of the tabernacle of the testimony