Tamid, Chapter 5, Mishnah 6. This chapter follows the morning service in the Beit Hamikdash step by step, and here the Mishnah pauses on one particular vessel and the sound it made.
In the Beit Hamikdash there was a keli called a magrefah, a shovel. It was built in such a way that when it was flung down onto the floor it produced an enormous noise. Our mishnah teaches how that noise was put to use during the morning service.
The Throw
"Higi'u bein ha'ulam vela'mizbeach": the Mishnah places us in the thick of the ketoret. Two kohanim had roles in that offering. In the hands of the first was the vessel holding the incense spices; the second carried the burning coals destined for the golden mizbeach that stood within the heichal. Together they crossed the azara in the direction of the heichal, until they reached the open space that separates the ulam from the outer mizbeach. Since the ulam is the antechamber standing directly before the heichal, these two kohanim are now poised on the very doorstep of the incense service.
"Natal echad et hamagrefah": at that point one of the pair lifted up the shovel, "vezorka", and flung it down, "bein ha'ulam vela'mizbeach", against the floor of that same open space in front of the ulam.
The Mishnah measures the volume for us: "Ein adam shomei'a kol chaveiro", a man could not catch the voice of the person he was speaking with, "biYerushalayim mikol hamagrefah", anywhere in the city, so long as the din of that shovel filled the air.
Three Purposes
"Ushlosha devarim hayta meshameshet": that sound served three separate functions.
First: "Kohen sheshomei'a et kola", a kohen who caught that sound, "yodei'a she'echav hakohanim", realized that his fellow kohanim were "nichnasim lehishtachavot", going inside to bow, "vehu ratz uva", and he would come running. The practice was that once the incense had been burned, whoever was serving in the courtyard would step into the heichal and prostrate together with the two who had performed the ketoret. A kohen still beyond the azara therefore learned from the crash that the moment of the incense had arrived, and he would hurry in so as not to miss bowing along with everyone else.
Second: "Uven Levi", and as for a Levi, "shehu shomei'a et kola", who heard that same sound, "yodei'a she'echav halevi'im", he understood that his fellow levi'im were "nichnasim ledaber bashir", coming in to take up the song, "vehu ratz uva", and he too would hurry over. The shir followed the nisuch hayayin, the pouring of the wine libation upon the mizbeach, and at that stage the levi'im lifted their voices together with their instruments. Any Levi who found himself outside the courtyard would therefore make his way in when the shovel crashed, so that he could join in praising Hashem.
Third: "Verosh hama'amad", the officer appointed over the kohanim of that day's watch, "haya ma'amid et hatemei'im", would station the men among them who were tamei, "besha'ar hamizrach", at the eastern gate. He placed them there deliberately in the open, where the public would notice them. The benefit came later: when these kohanim were seen walking off, nobody would imagine they were sneaking away before their time in order to look after private business. It would be obvious to all that a state of tumah had disqualified them from the avodah, and that this alone accounted for their leaving.