The seventh perek of Massekhet Yoma, which begins on today’s daf, opens with a description of the kohen gadol reading the command of the Yom Kippur service as it appears in the Torah (Vayikra 16:1-34; 23:26-32). The Jerusalem Talmud derives the need for this public reading from the passage “…and he did as God commanded Moshe,” which is understood to obligate not only performance of the avoda (Temple service), but also teaching about it.
The Mishna notes that the people who came to watch the Yom Kippur service needed to choose whether to attend the Torah reading or to go to see the burning of the sacrifices (the par and se’ir), which were done outside of Jerusalem, as was taught in the previous perek. According to the Rambam in his commentary to the Mishnah, the Mishna emphasizes this in order to teach that the rule forbidding someone to pass up the opportunity to perform one mitzva in order to do another (ein ma’avirin al ha-mitzvot) only applies to someone who is actually obligated in a mitzva, and not to someone who is simply observing the mitzva, even taking into consideration the idea that be-rov am hadrat melekh – that the King is honored before a large group.
The Torah reading described here only takes place after the se’ir ha-mishtale’ah – the scapegoat – has arrived at its destination in the desert, which is why the last Mishna in the sixth perek informs us that the kohen gadol waited for the signal that the mitzva of the se’ir had been accomplished. Three opinions are offered by the Mishna as to how the message was sent to the Temple. According to the Tanna Kamma, people were assigned to stand along the route to the desert. When the designated person completed his mission he would wave a flag, which would signal the next person along the line to do so, and each person would take up the signal until it reached the mikdash. Rabbi Yehuda argues that we know the distance to the desert is three Roman miles, so we merely need to measure out the time that it takes to walk that distance and we know that the mitzva has been done. Rabbi Yishma’el suggests that we would know it because the scarlet ribbon that was tied around the horns of the se’ir had a parallel ribbon tied in the Temple. When they turned white (based on the passage in Yeshayahu 1:18) it would be clear that the scapegoat had reached its final destination.
It appears that Rabbi Yehuda felt that we did not need conclusive proof, so the Tanna Kamma’s suggestion of using flags was unwieldy and unnecessary. The Tanna Kamma, however, accepts neither Rabbi Yehuda’s estimate, nor Rabbi Yishmael’s reliance on miracles.