All the service of the Gershonites—all their transport duties and other work—is to be done at the direction of Aaron and his sons; you are to assign to them all that they are responsible to carry.
KJV
At the appointment of Aaron and his sons shall be all the service of the sons of the Gershonites, in all their burdens, and in all their service: and ye shall appoint unto them in charge all their burdens.
ASV
At the commandment of Aaron and his sons shall be all the service of the sons of the Gershonites, in all their burden, and in all their service; and ye shall appoint unto them in charge all their burden.