1 Chronicles 23:5-7

YLT(i) 5 and four thousand gatekeepers, and four thousand giving praise to Jehovah, `with instruments that I made for praising,' saith David. 6 And David distributeth them into courses: Of the sons of Levi: of Gershon, Kohath, and Merari. 7 Of the Gershonite: Laadan and Shimei.