Numbers 1:1-3

1The Lord spoke [by special revelation] to Moses in the Wilderness of Sinai in the Tent of Meeting (tabernacle) on the first day of the second month in the second year after the Israelites came out of the land of Egypt, saying,

2“Take a census of all the congregation of the sons of Israel, by their families (clans), by their fathers’ households, according to the number of names, every male, head by head

3from twenty years old and upward, all in Israel who are able to go out to war. You and Aaron shall number them, army by army.