Reference

1 Chronicles 23:4

Of which, twenty and four thousand were to set forward the work of the house of the Lord; and six thousand were officers and judges:
2

And he gathered together all the princes of Israel, with the priests and the Levites.

3

Now the Levites were numbered from the age of thirty years and upward: and their number by their polls, man by man, was thirty and eight thousand.

4

Of which, twenty and four thousand were to set forward the work of the house of the Lord; and six thousand were officers and judges:

5

Moreover four thousand were porters; and four thousand praised the Lord with the instruments which I made, said David, to praise therewith.

6

And David divided them into courses among the sons of Levi, namely, Gershon, Kohath, and Merari.