Numbers 1:16-19

These were the men chosen from the people to be leaders of their tribes, the heads of Israel’s family groups. Moses and Aaron took these men who had been picked and called all the people of Israel together on the first day of the second month. Then the people were listed by their families and family groups, and all the men who were twenty years old or older were listed by name. Moses did exactly what the LORD had commanded and listed the people while they were in the Desert of Sinai.