|Positive Mitzvah Thirty-Six
Kohanim Ministering in Courses
Requires Beit HaMikdash
Kohanim are commanded to minister in Courses with every Course ministering one week, and that all Courses are not to minister at the same time, except during the Festivals, when all Courses are to share equally in the service and any Kohen who is present may sacrifice. The Courses in turn were subdivided into Fathers' Houses, and each House ministering one day out of the seven. (Tamid 1, 1)
David and Shmuel divided the Kohanim into twenty-four Courses (1Divrei HaYamim 24:4-18) and in Tractate Sukkah 55b it is explained that during the Festivals all the Courses shared equally in the service.