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 eighth 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.

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.

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 eighth 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.

We learned in the mishna with regard to all other offerings that one unwittingly slaughtered on Shabbat for the purpose of a Paschal offering, that if they were not fit for the Paschal offering, he is liable to bring a sin-offering, and if they were fit, Rabbi Eliezer deems him liable to bring a sin-offering, and Rabbi Yehoshua exempts him. The Gemara asks: Who is the tanna that distinguishes between offerings that are fit for the Paschal lamb and those that are not fit?

The Gemara explains: It is Rabbi Shimon, as it was taught in a baraita: If one unwittingly slaughters other offerings on Shabbat for the purpose of a Paschal offering, whether they are offerings that are fit for the Paschal lamb or they are offerings that are not fit, and similarly, if he unwittingly slaughters other offerings for the purpose of communal offerings on Shabbat, he is exempt from bringing a sin-offering; this is the statement of Rabbi Meir. Rabbi Shimon said: Rabbi Eliezer and Rabbi Yehoshua did not disagree about one who slaughtered offerings that are not fit, for in that case all agree that he is liable. With regard to what did they disagree? With regard to one who slaughtered offerings that are fit, for Rabbi Eliezer deems him liable to bring a sin-offering and Rabbi Yehoshua exempts him. This indicates that the unattributed ruling of our mishna is in accordance with the opinion of Rabbi Shimon.

Rav Beivai said that Rabbi Elazar said: Rabbi Meir would exempt him even in the case of a calf of a peace-offering that he slaughtered for the purpose of the Paschal offering, even though one does not ordinarily mistake a calf for a lamb. Rabbi Zeira said to Rav Beivai: But didn’t Rabbi Yoḥanan say that Rabbi Meir conceded that if one slaughtered blemished animals on Shabbat he is liable to bring a sin-offering? He said to him: With regard to blemished animals, he is not at all preoccupied with them, because he knows that they are ineligible to be offered as sacrifices. But as for this calf, he is preoccupied with sacrificing it as an offering, and he may therefore make a mistake.

Rava raised a dilemma before Rav Naḥman: If one unwittingly slaughtered an unconsecrated animal for the purpose of a Paschal offering, what would Rabbi Meir say? Would he exempt him in this case as well? Rav Naḥman said to him: Rabbi Meir would exempt him even if he slaughtered an unconsecrated animal for the purpose of a Paschal offering.

Rava asked him: But didn’t Rabbi Yoḥanan say that Rabbi Meir concedes that if one slaughtered blemished animals on Shabbat he is liable to bring a sin-offering, as they are never sacrificed as offerings, and similarly, unconsecrated animals are never sacrificed as offerings? Rav Naḥman responded: There is room for a distinction. Blemished animals cannot be confused with unblemished ones, and so there is no legitimate reason for error; but these, i.e., unconsecrated animals, can easily be confused with consecrated animals, as they are externally indistinguishable from one another, and therefore one who confuses them is exempt.

Rava asked further: And is Rabbi Meir’s reason really that these can be confused and these cannot be confused with a legitimate offering? But didn’t Rav Beivai say that Rabbi Elazar said that Rabbi Meir would exempt him even in the case of a calf of a peace-offering that he slaughtered for the purpose of the Paschal offering, even though there is no way to mistake a calf for an animal that can be brought for the Paschal offering? Therefore, it is apparent that Rabbi Meir’s reason is that he is preoccupied with sacrificing the calf as an offering, and consequently he is exempt if he erred and slaughtered it for the purpose of a Paschal lamb. But why should one be exempt if he brought an unconsecrated animal for the purpose of a Paschal offering? He is not preoccupied with bringing it as an offering.

Rav Naḥman said to him: Both reasons apply according to Rabbi Meir. If one is preoccupied with bringing the animal as an offering, he is exempt even though the animal cannot easily be confused with the one he was supposed to sacrifice. And when the animal can easily be confused with the one set aside as an offering, he is exempt, even though he is not preoccupied with bringing it as an offering. This comes to exclude blemished animals, which cannot be confused with unblemished animals and with whose sacrifice he is not preoccupied.

The Gemara relates that Rabbi Zeira and Rabbi Shmuel bar Rav Yitzḥak were sitting on the porch of Rabbi Shmuel bar Rav Yitzḥak, and they sat and said: Rabbi Shimon ben Lakish said: If one unwittingly confused a spit of leftover sacrificial meat, which it is prohibited to eat and which makes one liable to receive the punishment of karet when one eats it intentionally, with a spit of roasted sacrificial meat, which is a mitzva to eat, and he ate it, he is liable to bring a sin-offering. Although he intended to do a mitzva, since he unwittingly transgressed the prohibition against eating leftover sacrificial meat, he must bring a sin-offering.

And they further reported that Rabbi Yoḥanan said: If one unwittingly engaged in sexual intercourse with his wife while she was menstruating, he is liable to bring a sin-offering. But if he unwittingly engaged in sexual intercourse with his sister-in-law who was waiting to become his wife through levirate marriage while she was menstruating, he is exempt, because the act of intercourse itself is a mitzva. A man whose brother died without children is obliged by Torah law to marry his deceased brother’s widow and “come to her” (Deuteronomy 25:5), so that even if he mistakenly transgressed while attempting to fulfill the mitzva, he is exempt from bringing a sin-offering.

The Gemara attempts to determine whether Rabbi Yoḥanan agrees or disagrees with Reish Lakish’s ruling: Some say that all the more so in the first case, where one unwittingly ate a spit of leftover sacrificial meat, Rabbi Yoḥanan would deem him liable to bring a sin-offering, for he did not actually perform a mitzva when he ate the meat, even though he intended to do so. This stands in contrast to the second case, where the person unwittingly engaged in sexual intercourse with his wife while she was menstruating, where he at least performed a small mitzva, as will be explained shortly.

Others say that according to Rabbi Yoḥanan in that case where one ate leftover sacrificial meat, he is exempt from bringing a sin-offering. What is the reason? There, where he had sexual intercourse with his wife while she was menstruating, he is liable, for he should have asked her if she was menstruating, and because he failed to do so he is liable to bring a sin-offering. But here, where he ate a spit of leftover sacrificial meat, he did not have anyone to ask, and so he is not liable to bring a sin-offering.

The Gemara asks: And according to Rabbi Yoḥanan, what is different about one who unwittingly engaged in sexual intercourse with his sister-in-law, in that he is exempt from bringing a sin-offering? Is it that he performed a mitzva, i.e., the mitzva of levirate marriage? If so, then also in the case where he unwittingly engaged in sexual intercourse with his wife while she was menstruating, he performed a mitzva, for he occupied himself in the fulfillment of the mitzva of procreation. The Gemara answers that we are dealing here with a case where his wife is pregnant, such that intercourse cannot lead to procreation.

The Gemara raises another question: Nevertheless, there is the mitzva of the enjoyment of conjugal rights. One of a husband’s marital obligations is to engage in sexual intercourse with his wife at regular intervals (see Exodus 21:10), and this is considered a mitzva. The Gemara answers that we are talking about a case where it is not the time of her conjugal rights.

The Gemara asks further: Even so, didn’t Rava say that a man is obligated to please his wife through a mitzva? That is to say, he must engage in sexual intercourse with her when she so desires, even if it is not the time of her conjugal rights. The Gemara answers that we are dealing with a case where it was near her expected date of menstruation, when sexual relations are prohibited due to a concern that the woman may already be menstruating or that she may begin to menstruate during the sexual act.

The Gemara asks: If so, i.e., if they engaged in sexual intercourse near the woman’s expected date of menstruation when he should have refrained from doing so, then even in the case where he had sexual intercourse with his sister-in-law and she turned out to be menstruating, he should also be liable, as the mitzva of levirate marriage does not apply at that time. The Gemara explains that with regard to his sister-in-law, he is still shy [bazeiz] in front of her and uncomfortable asking her whether she is close to her expected menstruation date, whereas with regard to his wife, he is not shy in front of her, and so he should have asked her.

The Gemara asks: And Rabbi Yoḥanan, in accordance with whose opinion did he rule with regard to one who erred while engaged in a mitzva? If you say he ruled in accordance with the opinion of Rabbi Yosei, as we learned in a mishna: Rabbi Yosei says: If the first Festival day of the festival of Sukkot occurs on Shabbat, and he forgot and carried his lulav out into the public domain and continued to transport it there, unwittingly performing a prohibited labor, he is exempt from bringing a sin-offering. That is because he carried it out with permission, that is to say, he was acting with the intention of fulfilling a mitzva.

There is room to differentiate between Rabbi Yosei’s ruling and that of Rabbi Yoḥanan: Perhaps it is different there, as he is pressed for time. Since by Torah law the mitzva of lulav applies only one day a year, he is anxious to fulfill the mitzva and therefore does not realize that he is violating a Torah prohibition. This is unlike the case of levirate marriage, which need not be performed at any specific time and about which he is less pressured.

Rather, one might say that Rabbi Yoḥanan issued his ruling in accordance with the opinion of Rabbi Yehoshua in our mishna with regard to offerings, for according to Rabbi Yehoshua, one who unwittingly slaughtered another offering on Shabbat for the purpose of a Paschal offering, and the animal was fit to be brought as a Paschal offering, is exempt from bringing a sin-offering. Here too, however, there is room to differentiate. Perhaps there also we can say that Rabbi Yehoshua exempts him because he is pressed for time.

Rather, one might say that Rabbi Yoḥanan’s ruling is in accordance with the opinion of Rabbi Yehoshua with regard to babies, one that should have been circumcised on Shabbat eve and the other on Shabbat, and the circumciser forgot and circumcised the one that should have been circumcised on Shabbat eve on Shabbat. In that case the circumciser is exempt from bringing a sin-offering. But once again there is room to differentiate: Perhaps there too, Rabbi Yehoshua exempts him because he is pressed for time.

Rather, we should say that Rabbi Yoḥanan’s ruling is in accordance with the opinion of Rabbi Yehoshua with regard to teruma, as we learned in a mishna: If a priest was eating teruma, and it became known that he was the son of a divorced woman or a woman who underwent ḥalitza and he is therefore disqualified from the priesthood and may not eat teruma, Rabbi Eliezer deems him liable to pay the value of the principal and an additional fifth, like any non-priest who unwittingly ate teruma, whereas Rabbi Yehoshua exempts him. In this case, one who thought he was a priest and therefore fulfilling a mitzva when he ate the teruma was actually committing a transgression, but nevertheless, Rabbi Yehoshua exempts him from the ordinary penalty. On the face of it, this is similar to Rabbi Yoḥanan’s ruling.

This comparison can, however, be rejected, for perhaps that case should be explained in accordance with the opinion of Rav Beivai bar Abaye. For Rav Beivai bar Abaye said: The mishna is talking about a disqualified priest who ate teruma which is leaven on the eve of Passover, whose time is pressing, because if he does not eat it quickly he will have to burn it.

Alternatively, there may be another reason to differentiate: Eating teruma is different, because it is called sacred service, and the Merciful One validates service performed by someone of priestly descent even if he is not fit for the priesthood.

As we learned in a mishna: If a priest was standing and sacrificing offerings on the altar, and it became known that he was the son of a divorced woman or the son of a woman who underwent ḥalitza, all the offerings that he offered on the altar until that time are disqualified, because only service performed by a priest deemed fit is acceptable. And Rabbi Yehoshua validates them. And we said: What is the reason of Rabbi Yehoshua? As it is written with regard to the tribe of Levi: “Bless, Lord, his substance and accept the work of his hands” (Deuteronomy 33:11), which teaches that after the fact, God accepts the work of a priest’s hands, even if it becomes clear that he was actually disqualified at the time he performed the service.

The Gemara questions what was stated above: And where is teruma called service? The Gemara explains: As it was taught in a baraita: There was an incident involving Rabbi Tarfon, who did not come in the evening to the study hall. In the morning, Rabban Gamliel found him and said to him: For what reason did you not come in the evening to the study hall? He said to him: I was performing sacred service. He said to him: All your words are astonishing; from where do we have service in this time after the destruction of the Temple? He said to him: It says in Scripture: