They said to the Kohen Gadol, “The he-goat has reached the wilderness.” And how did they know that the he-goat had reached the wilderness? They set up watch-posts and waved cloths, and thus they knew that the he-goat had reached the wilderness.  R' Yehudah said: But they had a dependable signal: From Jerusalem to the place of the he-goat's sharp peak was three mil; they walked a mil, returned a mil, and tarried for [the time needed to walk] a mil. Thus they knew that the he-goat had reached the wilderness.  R' Yishmael says: But did they not have another sign? A strip of red wool was tied atop the Temple entrance, and when the he-goat reached the wilderness the strip of wool whitened, as it has been said: [Even] if your sins will be like crimson thread they will become white as snow.