Today's daf is dedicated to the release of Idan Alexander after 584 days in captivity. Wishing him a refuah shleima and praying for the safe release of the rest of the hostages. 

According to Rabbi Yochanan, Rabbi Shimon and the rabbis disagree about whether or not animals left over from the previous year that were designated for the Tamid sacrifice can be redeemed without a blemish. The Gemara tries to find a source for Rabbi Yochanan's understanding that the rabbis disagree with Rabbi Shimon, but they are not successful.

According to Rabbi Shimon, they cannot - so what does one do with them? If they were designated for communal burnt offerings, they would sacrifice them as voluntary communal offerings on the altar meant to keep the altar busy at all times. If they were designated for communal sin offerings, they could not be used directly as voluntary burnt offerings so they would wait until they were blemished, redeem them, and buy animals with the money to be sacrificed as voluntary burnt offerings. There is a concern that if this were to be permitted, one may think that one can change the destination even at an earlier stage (before the atonement for that sacrifice is achieved.  The rabbis bring three tannaitic sources to support this. Another braita is brought to support the explanation that the extra animals designated for the Tamid sacrifice are used for voluntary burnt offerings.

Can one purchase birds for the burnt offerings used to fill the altar?

Shmuel also held like Rabbi Yochanan that according to Rabbi Shimon, the extra animals could be used as voluntary burnt offerings.

What is the source for the fact that the goat offering brought inside on Yom Kippur atones also for intentional sins of impurity in the Temple?