Jamieson, Fausset and Brown on 1 Chronicles 25:8

8. they cast lots, ward against ward--"Ward" is an old English word for "division" or "company." The lot was cast to determine the precedence of the classes or divisions over which the musical leaders presided; and, in order to secure an impartial arrangement of their order, the master and his assistants, the teacher and his scholars, in each class or company took part in this solemn casting of lots. In the first catalogue given in this chapter the courses are classed according to their employment as musicians. In the second, they are arranged in the order of their service.