Numbers 1:17-19

17So Moses and Aaron took these men who had been designated by name, 18and they assembled all the congregation together on the 1first of the second month. Then they registered by 2ancestry in their families, by their fathers’ households, according to the number of names, from twenty years old and upward, head by head, 19just as 3the Lord had commanded Moses. So he numbered them in the wilderness of Sinai.