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.”