Numbers 7:3

7:3 They brought their offering before the Lord, six covered carts and twelve oxen – one cart for every two of the leaders, and an ox for each one; and they presented them in front of the tabernacle.

Numbers 7:7-8

7:7 He gave two carts and four oxen to the Gershonites, as their service required; 7:8 and he gave four carts and eight oxen to the Merarites, as their service required, under the authority of Ithamar son of Aaron the priest.