1 Chronicles 23:24-27

24These were the descendants of Levi by their families—the heads of families as they were registered under their names and counted individually, that is, the workers twenty years old or more who served in the temple of the Lord. 25For David had said, “Since the Lord, the God of Israel, has granted rest to his people and has come to dwell in Jerusalem forever, 26the Levites no longer need to carry the tabernacle or any of the articles used in its service.” 27According to the last instructions of David, the Levites were counted from those twenty years old or more.