1 Chronicles 23:4-8

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.

Of the Gershonites were, Laadan, and Shimei.

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