1 Chronicles 23:7 (KJV)

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

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.

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:

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

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

The sons of Laadan; the chief was Jehiel, and Zetham, and Joel, three.

The sons of Shimei; Shelomith, and Haziel, and Haran, three. These were the chief of the fathers of Laadan.

And the sons of Shimei were, Jahath, Zina, and Jeush, and Beriah. These four were the sons of Shimei.

And Jahath was the chief, and Zizah the second: but Jeush and Beriah had not many sons; therefore they were in one reckoning, according to their father's house.

The sons of Kohath; Amram, Izhar, Hebron, and Uzziel, four.