Yoma, Chapter Six, Mishnah Three
The mishnah now begins to describe what was done with the goat For Azazel.
They handed it over to him who was to lead it away.
All were fit to lead it away, but the priests made a fixed rule not to permit an Israelite to lead it away.
Rabbi Yose said: it once happened that Arsela led it away, although he was an Israelite.
Whereas the Torah simply states, And the goat shall be set free in the wilderness (Leviticus 16:22), the rabbis put forth an elaborate description of the process.
The first thing is that the goat is handed over to someone. This person can be anyone, even a non-priest, but the high priests established the practice that only other priests should be honored with this privilege. On the other hand, Rabbi Yose testifies that one time someone named Arsela lead the goat away and he wasnt a priest.