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 1:18

1:18 and they assembled the entire community together on the first day of the second month. Then the people recorded their ancestry by their clans and families, and the men who were twenty years old or older were listed by name individually,

Numbers 1:20

1:20 And they were as follows:

The descendants of Reuben, the firstborn son of Israel: According to the records of their clans and families, all the males twenty years old or older who could serve in the army were listed by name individually.

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 32:11

32:11 ‘Because they have not followed me wholeheartedly, not one of the men twenty years old and upward who came from Egypt will see the land that I swore to give to Abraham, Isaac, and Jacob,