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 14:29

14:29 Your dead bodies will fall in this wilderness – all those of you who were numbered, according to your full number, from twenty years old and upward, who have murmured against me.

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.”

Numbers 26:4

26:4 “Number the people from twenty years old and upward, just as the Lord commanded Moses and the Israelites who went out from the land of Egypt.”