Numbers 7:6-10

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

Two carts and four oxen he gave to the sons of Gershon, according to their service,

and four carts and eight oxen he gave to the sons of Merari, according to their service, under the direction of Ithamar the son of Aaron the priest.

But he did not give any to the sons of Kohath, because theirs was the service of the holy objects, which they carried on the shoulder.

And the leaders offered the dedication offering for the altar when it was anointed, so the leaders offered their offering before the altar.