I Chronicles 23:1-5

So when David was old and full of days, he made his son Solomon king over Israel. And he gathered together all the leaders of Israel, with the priests and the Levites. Now the Levites were numbered from the age of thirty years and above; and the number of individual males was thirty-eight thousand. Of these, twenty-four thousand were to look after the work of the house of the LORD, six thousand were officers and judges, four thousand were gatekeepers, and four thousand praised the LORD with musical instruments, “which I made,” said David, “for giving praise.”