Numbers 1:1-3

1The Lord spoke to Moses in the tent of meeting in the Desert of Sinai on the first day of the second month of the second year after the Israelites came out of Egypt. He said:

2“Take a census of the whole Israelite community by their clans and families, listing every man by name, one by one.

3You and Aaron are to count according to their divisions all the men in Israel who are twenty years old or more and able to serve in the army.