The Levites: David: Subdivided Into 24 Courses
Source: TTT
1 Chronicles 23:6
Then David divided the Levites into divisions according to the sons of Levi: Gershom, Kohath, and Merari.
1 Chronicles 25:8–31
They cast lots for their duties, young and old alike, teacher as well as pupil. / The first lot, which was for Asaph, fell to Joseph, his sons, and his brothers—12 in all; the second to Gedaliah, his sons, and his brothers—12 in all; / the third to Zaccur, his sons, and his brothers—12 in all;