Yoma, Chapter Six, Mishnah Six
This mishnah concludes the epic saga of the goat sent out to the wilderness. Alas, it will not end well for the goat (so gentle souls imagining the goat being set free to find its familybe warned). However, hopefully the goats demise will not be in vain and it will aid in bringing atonement to the children of Israel.
1) What did he do? He divided the thread of crimson wool, and tied one half to the rock, the other half between its horns, and pushed it from behind, and it went rolling down and before it had reached half its way down hill it broken into limbs.
2) He came back and sat down under the last booth until it grew dark.
3) And from when are his clothes unclean?
a) From the moment he has gone outside the walls of Jerusalem.
b) Rabbi Shimon says: from the moment he pushes it into Zuk.
Section one: When he would reach Zuk, the priest accompanying the goat would divide the crimson wool which was tied to the goats horn (see above 4:2) into two sections. One side he would tie to the goats horns and the other side he would tie to the rock. Mishnah eight below will explain that there was a tradition that when the goat reached the wilderness the crimson wool would turn white, to symbolize Gods cleansing of Israel of its sins. The Talmud explains that he would tie the thread to the rock so that he could see it turn white.
After having tied the thread to the rock, the priest would push the goat off the cliff, where it would die rather quickly.
Section two: The priest now finds himself at Zuk with a Shabbat border limit of only 2000 cubits, not enough to reach the last sukkah. Nevertheless, since it was considered dangerous to remain in the wilderness alone, the rabbis allowed him to walk the 4000 cubits back to the last sukkah. However, he cant go any further than that until Yom Kippur is over.
Section three: Leviticus 16:26 says that the one who sent the goat to Azazel must wash his clothes and bathe his body. This implies that his clothes were rendered impure. Our mishnah asks when is this so and it provides two opinions. The first opinion is that the clothes are impure from the time he leaves the walls of Jerusalem. This might imply that the goat has in a certain sense fulfilled its function at this early stage. Rabbi Shimon holds that the clothes are not impure until the goat has been pushed off of Zuk.