Masechet Tamid, Chapter 7, Mishnah 1. With the offering of the ketoret, the service of the korban tamid has reached its conclusion. That may sound surprising, since the limbs of the tamid animal have not yet been placed upon the mizbeach, and our Mishnah in the chapter will still describe those steps in Mishnah 3. Nevertheless, the tamid service was regarded as complete once the ketoret was brought, even if what follows had never taken place.
At that point the kohanim who had taken part in the service would enter the Heichal and prostrate themselves, each one bowing as his own task came to an end. The others would then come in, one after another, and bow as well, now that the morning service had been completed. And if the Kohen Gadol was among those serving, the honor of entering the Heichal first was extended to him, with the remaining kohanim following afterward.
Three Kohanim Escort Him
Our Mishnah states: "bizman sheKohen Gadol nichnas lehishtachavot", meaning that whenever the High Priest went inside ahead of all his fellow kohanim in order to prostrate himself, "shelosha ochazim bo", a trio of kohanim went with him and steadied him along the way. Picture a monarch of great stature: he never travels unaccompanied, but is attended by servants alert to whatever he might require. Lehavdil, so it was with the Kohen Gadol, supported and escorted by others as he made his way.
"Echad bimino ve'echad bismolo ve'echad ba'avanim tovot." The first of the three took his place at the Kohen Gadol's right side, the second at his left, while the third walked immediately behind him, taking hold of the gems mounted on the shoulder straps of the ephod, that apron-like vestment worn by the Kohen Gadol.
The Curtain of the Ulam
As soon as he had gone inside, the memuneh would pull shut the drape of the Ulam, the antechamber positioned directly in front of the Heichal. On an ordinary day that drape was left open for the whole of the daylight hours, but here it was drawn so that the Kohen Gadol would not be exposed to view. His standing before HaKadosh Baruch Hu was fittingly a moment of solitude.
Once his bowing was done and the time came for him to leave, that same appointed kohen, the memuneh, would raise the drape again. In the words of the Mishnah: "Vecheivan sheshama hamemuneh kol raglav shel Kohen Gadol shehu yotze, higbia lo et haparochet." But how did he know the moment had arrived? Small golden bells hung along the hem of the Kohen Gadol's robe, and their ringing as he walked gave notice that he was leaving, whereupon the appointed one lifted the drape of the Ulam and let him pass through.
Then the Rest
"Nichnas vehishtachava veyatza." Once the Kohen Gadol had gone out, the memuneh himself entered the Heichal, bowed down, and left. He too was granted precedence over the other kohanim, for he had served and directed the entire order of the morning service.
"Venichnasu echav hakohanim vehishtachavu veyatzu." Only then did his fellow kohanim enter the Heichal, prostrate themselves, and take their leave.