Numbers 7:3-9

3And they brought their offering before the LORD, six covered wagons, and twelve oxen; a wagon for two of the princes, and for each one an ox: and they brought them before the tabernacle. 4And the LORD spoke to Moses, saying, 5Take it of them, that they may be to perform the service of the tabernacle of the congregation; and thou shalt give them to the Levites, to every man according to his service. 6And Moses took the wagons and the oxen, and gave them to the Levites. 7Two wagons and four oxen he gave to the sons of Gershon, according to their service: 8And four wagons and eight oxen he gave to the sons of Merari, according to their service, under the hand of Ithamar the son of Aaron the priest. 9But to the sons of Kohath he gave none: because the service of the sanctuary belonging to them was that they should bear upon their shoulders.