Lamentations: Third Kinah Fourth Stanza Line 2
“The discontinuation of the watches”: The Talmud says that King David and the prophet Samuel divided the Kohanim into 24 families that would alternate service in the Beis Hamikdash.
The Leviim were also divided so that they could alternate turns in Jerusalem. The law demands that a “zar” someone who is not a Kohen or Levi be present at each communal sacrifice. The entire nation was therefore also divided into shifts and each shift would send representatives to Jerusalem twice a year to be present at the daily sacrifice.
The Beis Hamikdash was for all Jews to be active participants. The Cohanim and Leviim were not supposed to be distant from the people, representing them without the participation of everyone. All Jews were “present” and played a role.
The Beis Hamikdash was not an abstract place where “holy” people served God. It was literally the home for all the people. They all functioned there as active participants. It was clear to everyone that the Kohanim and Leviim functioned for them. When the Beis Hamikdash was destroyed we lost this sense of all being equally involved.