Temurah 24A

אבל בתרי סדרי לא, קא משמע לן.

But in a case where one designates two distinct sets of money, such as an additional set of money as a guarantee, R' Shimon does not state that the surplus money is allocated for communal gift offerings. R' Ami therefore teaches us that even in this case, R' Shimon agrees that the surplus money is allocated for communal gift offerings.

אמר רבי הושעיא: המפריש שתי חטאות לאחריות, מתכפר באחת מהן, וחבירתה רועה.

§ R' Hoshaya says: In the case of one who designates two animals as sin offerings as a guarantee, so that if one animal is lost he will achieve atonement with the other animal, he achieves atonement with one of them, and the other is left to graze until it develops a blemish. It is then sold, and the money received from its sale is used to purchase communal gift offerings.

אליבא דמאן? אילימא אליבא דרבנן ⁠— השתא המפריש לאיבוד, אמרי רבנן לאו כאיבוד דמי, לאחריות מיבעיא?!

The Talmud asks: In accordance with whose opinion does R' Hoshaya state this halakha? If we say that it is in accordance with the opinion of the Rabbis, then it is unnecessary. The Talmud explains: Now that in a case where one designates a sin offering instead of one that was lost, the Rabbis say that it is not considered like the lost animal, and it is therefore left to graze, is it necessary to state that in a case where one designates an additional sin offering as a guarantee, the second animal is left to graze?

אלא אליבא דרבי שמעון, האמר רבי שמעון: חמש חטאות מתות!

Rather, you will say that R' Hoshaya states this halakha in accordance with the opinion of R' Shimon. But didn’t R' Shimon say that there are 5 sin offerings that are left to die, one of which is a sin offering whose owner has achieved atonement with another animal? If so, even in a case where one designated an additional animal as a guarantee, once the owner has achieved atonement the remaining animal is left to die.