1 Chronicles 23:5-7

Darby(i) 5 and four thousand were doorkeepers; and four thousand praised Jehovah with the instruments which I made, [said David,] to praise [therewith]. 6 And David divided them into courses according to the sons of Levi: Gershon, Kohath, and Merari. 7 Of the Gershonites: Laadan and Shimei.