daf bit: Yoma 62

The torah commands that on Yom Kippur the high priest casts lots over two goats, one to be sent away with the people's sins ("for Azazel") and the other to be offered on the altar. The mishna says that the goats must be identical in appearance and value and that they must be bought at the same time. (But if any of that doesn't happen, it's still valid.) Now, what happens if one of the goats then dies prematurely? If this happens before the lots are cast they buy another goat; if it happens after the lots are cast, they buy two more goats and start over. But this leaves us with an extra goat; what happens there? The other goat of the original pair is put out to pasture until it acquires a blemish (which renders it unfit for the altar), at which point it is sold with the proceeds going to the temple. This is because once it has been designated for temple use it can't be put to some other purpose. (62a)