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 17:2

17:2 “Speak to the Israelites, and receive from them a staff from each tribe, one from every tribal leader, twelve staffs; you must write each man’s name on his staff.

Numbers 17:6

17:6 So Moses spoke to the Israelites, and each of their leaders gave him a staff, one for each leader, according to their tribes – twelve staffs; the staff of Aaron was among their staffs.