1 Chronicles 23:1-5

When David reached old age, he made his son Solomon king over Israel. And he assembled together all the leaders of Israel with the priests and Levites. The Levites thirty years old and upward were counted, and their number man by man was 38,000. Of these 24,000 were to oversee and inspect the work of the house of the LORD and 6,000 were to be administrators and judges, and 4,000 were gatekeepers, and 4,000 [musicians] were to praise the LORD with the instruments which David made for giving praise.