1 Chronicles 23:3-6

The Levites thirty years old or more were counted, and the total number of men was thirty-eight thousand. David said, “Of these, twenty-four thousand are to be in charge of the work of the temple of the LORD and six thousand are to be officials and judges. Four thousand are to be gatekeepers and four thousand are to praise the LORD with the musical instruments I have provided for that purpose.” David separated the Levites into divisions corresponding to the sons of Levi: Gershon, Kohath and Merari.