Why was this necessary? Because one time the moon's light rose and they thought that the east had lit up, so they slaughtered the daily sacrifice, and then [had to] take it out to the place of burning.  They took the Kohen Gadol down to the mikveh.  This was the rule in the Temple: Whoever moved his bowels needed immersion, and whoever urinated needed to wash his hands and his feet.

No person may enter the Temple Courtyard for service, even if he is tahor, until he immerses himself [in a mikveh].  On this day, the Kohen Gadol immerses himself five times and washes [his hands and feet] ten times, all of them in the Holy atop the Parvah Chamber, except for this one only.

They spread a linen sheet between him and the people. He undressed, descended, immersed himself, ascended, and dried himself. They brought him golden vestments, and he donned them; then he washed his hands and feet. They brought him the daily offering. He made the incision and another completed the slaughter for him. He received the blood [in a vessel] and threw it.  He entered [the Temple] to burn the morning incense, and to prepare the lamps [of the Menorah]. He offered the head and the limbs, the chavitin meal offering and the wine.

The morning incense was offered [every day] between the [throwing of the] blood and the [offering of the] limbs [of the daily offering]; that of the afternoon, between the [offering of the] limbs and the nesachim.  If the Kohen Gadol was old or delicate, they warmed water for him and poured it into the cold water so that it should lose its chill.