Numbers 7:5-9

Take it of them, that they may be to do the service of the tabernacle of the congregation; and thou shalt give them unto the Levites, to every man according to his service.

And Moses took the wagons and the oxen, and gave them unto the Levites.

Two wagons and four oxen he gave unto the sons of Gershon, according to their service:

And four wagons and eight oxen he gave unto the sons of Merari, according unto their service, under the hand of Ithamar the son of Aaron the priest.

But unto the sons of Kohath he gave none: because the service of the sanctuary belonging unto them was that they should bear upon their shoulders.