Pesachim 72B

שלא נתנה שבת לדחות. [וסיפא ⁠— נתנה שבת לדחות אצלו].

In that case, Shabbat does not stand to be overridden at all. Since the baby who should have been circumcised on Shabbat was already circumcised, and the only one left is the baby who should have been circumcised on Friday, the circumciser should have known that he has no circumcisions to perform on Shabbat, because a circumcision that was delayed beyond the 8th day does not override Shabbat. Therefore, he is liable if he performed the circumcision on Shabbat. In the latter clause, however, the circumcision was performed in a situation where Shabbat stands to be overridden for him, as the baby who should have been circumcised on Shabbat was not yet circumcised.

הכא ⁠— הרי נתנה שבת לדחות אצל קרבן ציבור.

Based on the understanding that everything depends on whether or not Shabbat stands to be overridden, it may be argued that here too, Shabbat stands to be overridden with regard to a communal offering. Therefore, one who on Shabbat unwittingly slaughters other offerings for the purpose of communal offerings is exempt from bringing a sin-offering, because he knows that communal offerings must be brought on Shabbat, and consequently there is some justification for his error.

אמר ליה רב אשי לרב כהנא: הכא נמי, הרי נתנה שבת לדחות אצל תינוקות דעלמא! אמר ליה: לגבי דהאי גברא מיהת לא איתיהיב.

Rav Ashi said to Rav Kahana that this explanation is difficult: Here too, it may be argued that Shabbat stands to be overridden with regard to babies in general, as it is permitted to circumcise a baby whose 8th day occurs on Shabbat, and so there is some minimal justification for his mistake. Rav Kahana said to him: That is indeed so. However, with regard to this person, Shabbat does not stand to be overridden, as there is no longer any child who is supposed to be circumcised on Shabbat. Therefore, if he unwittingly performed a circumcision on Shabbat, it is not considered as if he performed a transgression while preoccupied with the performance of a mitzva.