1 Chronicles 23:3

23:3 The Levites who were thirty years old and up were counted; there were 38,000 men.

1 Chronicles 23:27

23:27 According to David’s final instructions, the Levites twenty years old and up were counted.

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 4:3

4:3 from thirty years old and upward to fifty years old, all who enter the company to do the work in the tent of meeting.

Numbers 8:24

8:24 “This is what pertains to the Levites: At the age of twenty-five years and upward one may begin to join the company in the work of the tent of meeting,

Ezra 3:8

3:8 In the second year after they had come to the temple of God in Jerusalem, in the second month, Zerubbabel the son of Shealtiel and Jeshua the son of Jozadak initiated the work, along with the rest of their associates, the priests and the Levites, and all those who were coming to Jerusalem from the exile. They appointed the Levites who were at least twenty years old to take charge of the work on the Lord’s temple.