The Temple service and the sacrifices were on behalf of everybody. Can people go about their business as if nothing is happening? For that reason, the appointed members of the congregation were doing "maamadot" or "standing by" - as community representatives.
Now, the whole procedure was as follows. When the appointed week for each priest group would come, they would go to the Temple. However, half of them went to the labor market in Jericho to do agricultural work, which was plentiful and provided sustenance for the priests who served in the Temple. Some say that they would change after three days so that everybody would get a chance for Temple service. There were twenty-four groups of priests in total, and thus they would serve in the Temple two weeks a year on average.
The community representative would be standing by, saying prayers, reading from the Torah, and fasting. Some were in Jerusalem, but some remained in their cities, collecting themselves in the synagogue. Each group was essential, and the sacrifices could not be brought if it was missing.
The Temple service was what assured the existence of Heaven and the Earth. What is the source for this? In the phrase, "Whereby shall I know that I will inherit Israel?" The complete conversation went like this. Abraham said, "Master of the Universe! All is well now, but if Jews sin, will you destroy them?" God said, "No." Abraham continued, "How do I know?" God said, "Take three calves and three goats, etc." This means that the merit of the sacrifices will atone."
Art: Weaning the Calves by Rosa Bonheur