Numbers 1:3

1:3 You and Aaron are to number all in Israel who can serve in the army, those who are twenty years old or older, by their divisions.

Numbers 1:45

1:45 All the Israelites who were twenty years old or older, who could serve in Israel’s army, were numbered according to their families.

Numbers 3:8

3:8 And they are responsible for all the furnishings of the tent of meeting, and for the needs of the Israelites, as they serve in the tabernacle.

Numbers 26:2

26:2 “Take a census of the whole community of Israelites, from twenty years old and upward, by their clans, everyone who can serve in the army of Israel.”