Numbers 1:17-19

1:17 So Moses and Aaron took these men who had been mentioned specifically by name, 1:18 and they assembled the entire community together on the first day of the second month. Then the people recorded their ancestry by their clans and families, and the men who were twenty years old or older were listed by name individually, 1:19 just as the Lord had commanded Moses. And so he numbered them in the wilderness of Sinai.