All the service of the sons of the Gershonites shall be at the command of Aaron and his sons, in all that they are to carry and in all that they have to do. And you shall assign to their charge all that they are to carry.
We have here the charge of the other two families of the Levites, which, though not so honourable as the first, yet was necessary, and was to be done regularly. 1. The Gershonites were charged with all the drapery of the tabernacle, the curtains, and hangings, and the coverings of badgers' skins, Num 4:22-26.
Commenting on Numbers 4:21-33
From thirty years old and upward,.... The Septuagint version here, and in Num 4:3, renders it, from twenty five years old and upward, agreeable to Num 8:24, at the which age the Levites went into the tabernacle, to wait and to learn their business, but they did not enter upon it till thirty: even unto fifty years old shalt thou number them; at which age...
Num 4:27 Their service was to be performed “according to the mouth (i.e., according to the appointment) of Aaron and his sons, with regard to all their carrying (all that they were to carry), and all their doing.” - “And ye (the priests) shall appoint to them for attendance (in charge) all their carrying,” i.e., all the things they were to carry. בּמשׁמרת פּקד, to give into keeping.