Shevuot 11B

וכן שעירי עבודה זרה שאבדו והפריש אחרים תחתיהן ⁠– כולן ימותו. דברי רבי יהודה. רבי אלעזר ורבי שמעון אומרים: ירעו עד שיסתאבו, וימכרו ויפלו דמיהן לנדבה. שאין חטאת צבור מתה.

and likewise, goats that were designated to atone for an act of unwitting public idol worship that were lost, and one separated and sacrificed others in their stead, in such cases, all of the lost animals, should they subsequently be found, should be left to die. This is in accordance with the halakha that a sin-offering whose owner has already achieved atonement is left to die. This is the statement of R' Yehuda. R' Elazar and R' Shimon say: They should graze until they become unfit by developing a blemish, and then they are sold and their proceeds are allocated for communal gift offerings. They are not left to die, because the halakha is that a communal sin-offering is not left to die.

ואמאי? לימא לב בית דין מתנה עליהן!

Abaye explains his challenge: But why should it even be necessary to wait until the offerings develop a blemish? Let us say here also that the court tacitly stipulates concerning them, so that if it ultimately emerges that they were not needed, then they should have only sanctity that inheres in their value, and therefore it should be possible to redeem them even if they do not develop a blemish.

אבודין קאמרת? שאני אבודין, דלא שכיחי.

Rabba deflects the challenge: Did you say that there is a proof from the case of lost animals? Cases of lost animals are different, because they are not common. Therefore, the court does not stipulate concerning such an eventuality.

הרי פרה, דלא שכיחא, ותניא: פרה נפדית על כל פסול שבה ⁠– מתה תפדה, נשחטה תפדה, מצא אחרת נאה הימנה תפדה. שחטה על גבי מערכתה ⁠– אין לה פדייה עולמית! שאני פרה, דקדשי בדק הבית היא.

Abaye persists: But consider the case of a red heifer, which is not common, and yet it is taught in a baraita: A red heifer may be redeemed for any disqualification that occurs to it. If it died, it should be redeemed; if it was slaughtered in an improper place, it should be redeemed; if another was found that is choicer than it, it should be redeemed. But once the priest has slaughtered it properly on its arrangement of wood on the Mount of Olives, it can no longer be redeemed. Presumably, the reason it may be redeemed if a choicer one is found is that the court tacitly stipulates that in such a case it should be consecrated with sanctity that inheres in its value. It is apparent that even in uncommon cases, the court makes such stipulations. Rabba rejects the proof: The red heifer is different, as in all cases it has only the sanctity of items consecrated for Temple maintenance, which inheres only in the item’s value, and so it can always be redeemed, even if still unblemished.