These were the sons of Levi by their fathers' houses--the heads of the fathers' houses as they were counted individually by the number of their names, who did the work for the service of the house of the LORD, from the age of twenty years and above.
1 Chronicles 23:24
Surrounding context
23:23 The sons of Mushi were Mahli, Eder, and Jeremoth--three in all.
23:24 These were the sons of Levi by their fathers' houses--the heads of the fathers' houses as they were counted individually by the number of their names, who did the work for the service of the house of the LORD, from the age of twenty years and above.
23:25 For David said, "The LORD God of Israel has given rest to His people, that they may dwell in Jerusalem forever";