Pesachim 97B

כדרבי אושעיא. דאמר רבי אושעיא: הפריש שתי חטאות לאחריות ⁠— מתכפר באחת מהן, ושניה תרעה.

The Talmud answers: Even according to R' Yehuda HaNasi there is a case in which a sin-offering is left to graze, in accordance with the opinion of R' Oshaya, as R' Oshaya said: If one separated two sin-offerings from the outset as a guarantee, so that if one is lost he may gain atonement with the other, he gains atonement with one of them and the second is left to graze.

והא אילו בפסח כי האי גוונא קרב שלמים! אלא שמואל כרבי שמעון סבירא ליה, דאמר: חמש חטאות מתות.

The Talmud challenges this: But with regard to a Paschal lamb, in a case like this the second animal would be sacrificed as a peace-offering. This, too, does not follow Shmuel’s principle. Rather, it can be explained that Shmuel held in accordance with the opinion of R' Shimon, who said there are 5 sin-offerings that are left in isolation to die, including all those which are lost or deferred.

והא רועה לרבי שמעון לית ליה כלל! שמואל נמי חדא קאמר: כל שבחטאת מתה ⁠— בפסח קרב שלמים.

The Talmud asks: But R' Shimon does not concede in any case at all that a sin-offering is left to graze, as he holds that any sin-offering which is deferred for any reason is left to die, while Shmuel referred to sin-offerings left to graze. The Talmud answers: Shmuel also said only one case. He did not mention sin-offerings that are left to graze; he said only that with regard to any offering that became unfit such that a sin-offering in its condition would be left to die, if it is a Paschal lamb in that condition it is sacrificed as a peace-offering.

ומאי קא משמע לן? לאפוקי מדרבי יוחנן, דאמר: אין הפסח קרב שלמים אלא שנמצא אחר שחיטה, אבל קודם שחיטה ⁠— לא. אלמא: שחיטה קבע. קא משמע לן: חצות קבע.

The Talmud asks: And what does he teach us with this statement beyond what was taught explicitly in the Mishnah? The Talmud answers that Shmuel’s statement was meant to exclude the opinion of R' Yoḥanan, who said that a Paschal lamb is sacrificed as a peace-offering only when it is found after slaughter, but if it is found before the slaughter, no, it is not sacrificed as a peace-offering. Apparently, R' Yoḥanan held that the slaughter determines when a sacrifice is deferred; therefore, Shmuel teaches us that in his opinion midday determines whether it is considered deferred, even if the other animal has not yet been slaughtered, because midday is the time when it may be slaughtered. Consequently, if the Paschal lamb is still lost at midday, it may be offered as a peace-offering when it is found.