Me’ilah 26 - The First Service of the Day (Tamid)
The first service of the day in the Temple was "separation of the ashes." Since the Torah said, " and he will separate the ash… and place it beside the Altar ," the Kohen would go up on the Altar, scoop a shovelful of ash, then come down, and deposit it to the east of the Altar ramp. Any Kohen who wanted to do this service would wake up early, immerse himself in a mikveh, and be ready before the Kohen appointed over the distribution of services arrives. If more than one Kohen wanted to do the service, they would draw lots.
At what time did the appointed Kohen arrive? Sometimes a little before, and sometimes a little after the rooster’s cry. He would knock upon the Temple gates, and they would open it for him. He would say to them, "Whoever has immersed himself, should come and participate in the lottery." They made a lottery (we will learn about this in the tractate Yoma), and whoever won, won.
Art: Carl Jutz - Rooster with Hens and Chicks