Numbers 7:6-9

6So Moses took the carts and the oxen and gave them to the Levites.

7He gave two carts and four oxen to the sons of Gershon, according to their service [in transporting the tabernacle];

8and he gave four carts and eight oxen to the sons of Merari, according to their service [in transporting the tabernacle], under the supervision of Ithamar the son of Aaron, the [high] priest.

9But to the sons of Kohath he gave nothing, because they were assigned the care of the holy things which they carried on their shoulders [when the tabernacle was moved].