Tamid, Chapter 2, Mishnah 5. This chapter has been following the kohanim through the early morning service on the mizbe'ach: clearing away the ashes, arranging the great fire, and adding the wood for the day's offerings. Our mishnah now turns to a second, smaller fire that was built alongside the first one, a fire whose entire purpose was to produce the coals for the ketoret, the incense offered inside the heichal.
"Bareru misham atzei te'enah yafim": the Beit Hamikdash kept a chamber set aside for its supply of wood, and there the kohanim would sift through the pile and select sound, attractive logs of fig. "Lesader hama'arachah sheniyah laketoret": from these logs a second woodpile was arranged. Its flames would reduce the wood to glowing embers, and it was upon those embers that the incense would be offered.
Why specifically fig wood
Fig was not selected at random. The snake drew Adam and Chavah into their sin through slanderous speech, and once they had eaten it was fig leaves that they gathered to cover their exposure and their shame. The ketoret is precisely the offering that atones for lashon hara. There is a fittingness, then, in taking the embers that consumed the incense from the very tree whose leaves supplied that first covering.
Where the fire stood and how much it produced
"Mikeneged keren ma'aravit deromit": this second woodpile was positioned facing the southwestern corner of the altar. "Mashuch min hakeren": it was set back from that corner, "kelapei tzafon arba amot": four amot in a northerly direction.
"Be'omed chamesh se'im gechalim": when the logs had burned through, what remained was five se'ah of embers, a quantity of roughly seventeen gallons in our measurements. Some of these embers were carried inside the heichal so that the incense could be offered upon them.
"Uveshabbat be'omed shemoneh se'im gechalim": on Shabbat this woodpile was arranged on a larger scale, with thicker logs, so that eight se'ah of embers would remain when it burned down. The additional quantity was called for by the lechem hapanim: "shesham hayu notnin shenei bezichei levonah shel lechem hapanim." Every Shabbat two bezichim, two vessels of levonah that had been set beside the showbread, were burned, and they too needed embers of their own. The pile was therefore expanded so that there would be enough for all of it.
Returning the unconsumed portions
"Ha'evarim vehapedarim shelo nit'akelu meba'erev": whatever limbs and fats of the previous day's offerings the fire had not finished consuming through the night had earlier been shifted off to the side of the altar, as the opening mishnah of this chapter described, in order to clear the surface for building the fresh woodpile. "Machazirin otan lama'arachah": they were now lifted back onto the main arrangement, so that the fire would consume them entirely.
"Hitzitu shetei hama'arachot ba'esh": they kindled both arrangements, the great fire and the fire of the ketoret. "Veyardu uva'u lahem lelishkat hagazit": then they descended from the mizbe'ach and made their way to Lishkat Hagazit, where the next lottery for the day's services would be held.