Half of them lived in Jerusalem and half in Jericho, to provide food for the Jerusalemite half of the shift: Taanit 27a
It is a necessity to have members of Kohanim, Levites, and plain Jews in the shift: Taanit 27a
The regular shift was established as an Institution of the Prophets: Taanit 26a, 27a
The shift for the Closing Service of the Day was a rabbinic institution: Taanit 28a
Their Job
Source for having the Shifts: Taanit 26a, 27a
Praying in the main road of the town: Megillah 26a
They received a Blessing via the Hands of the Kohanim 4 times daily: Taanit 26a
Special Daily Torah Readings: Taanit 26a, 27b; Megillah 22a, 30b
Reading a section which is relevant to the day: Megillah 29a, 30b
How the Reading of the Torah was done: Taanit 27b-28a
Whether one person read at the afternoon service, or all read individually: Taanit 28a
Special fasts for the benefit of sailors, travellers in the desert, infants, and pregnant and nursing women: Taanit 27b
Shaving during the shift: Moed Katan 14a
Laundering during the shift: Moed Katan 14a
Reason for the above two lines: Moed Katan 14a
Laundering/Shaving on Thursdays, in honor of Shabbos: Moed Katan 14a
Suspension of the Shift or its Jobs
Suspension of the Shift on Friday afternoon: Taanit 26a
Suspension of specific prayers if Hallel-Prayer is recited: Taanit 26a, 28a-b
Suspension of specific prayers if Special Additional [Musaf] Offerings are brought: Taanit 26a, 28a-b
Suspension of specific prayers if the Offering of the Bringers of Wood for the Altar is brought: Taanit 26a, 28a
Suspension of Fasts on Friday in honor of Shabbat: Taanit 27b
Suspension of Sunday fasts: Taanit 27b The Mitzvah of Reading the Purim Story, vs the Prayers of the Shifts of non-Levites Representing the Nation on their Offerings: Megillah 3a
Beyond the Laws
Avraham was promised that his children would not be destroyed for their sins, in the merit of the Shifts: Taanit 27b
If not for the Shifts, the world would have been destroyed: Taanit 27b; Megillah 31b
