1 Chronicles 23:2-5

And he gathered together all the leaders of Israel with the priests and the Levites. The Levites were numbered from thirty years old and upward, and their number by census of men was 38,000. Of these, 24,000 were to oversee the work of the house of the LORD; and 6,000 were officers and judges, and 4,000 were gatekeepers, and 4,000 were praising the LORD with the instruments which David made for giving praise.