Numbers 7:6-9

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

7He gave two carts and four oxen to the Gershonites, as their service required;

8and he gave four carts and eight oxen to the Merarites, as their service required, under the authority of Ithamar son of Aaron the priest.

9But to the Kohathites he gave none, because the service of the holy things, which they carried on their shoulders, was their responsibility.