Numbers 1:1-3

1On the first day of the second month of the second year after the Israelites had come out of the land of Egypt, the LORD spoke to Moses in the Tent of Meeting in the Wilderness of Sinai. He said: 2“Take a census of the whole congregation of Israel by their clans and families, listing every man by name, one by one.

3You and Aaron are to number those who are twenty years of age or older by their divisions—everyone who can serve in Israel’s army.