The Gemara raised an objection to Rabbi Zeira from a baraita: If one consummates a levirate marriage with his yevama and seven months later she gives birth, there is uncertainty whether the child is nine months old and is the offspring of the first husband, or whether the child is only seven months old and is the offspring of the latter husband, i.e., the yavam. In such a case he must divorce her, but the offspring is of unflawed lineage. And to atone for the possibility that they engaged in forbidden intercourse, they are each obligated to bring a provisional guilt offering. The Gemara answers: In accordance with whose opinion is this baraita? It is in accordance with the opinion of Rabbi Eliezer.

The Gemara raised another objection to Rabbi Zeira from a mishna (Nidda 14a): If blood was found on her cloth immediately after intercourse, the woman and her husband are impure for seven days and are each liable to bring a sin offering. If blood was found on her cloth after time passed, they are both impure due to uncertainty and they are exempt from bringing the sin offering. And it is taught with regard to this last case that they are each liable to bring a provisional guilt offering. The Gemara again answers: In accordance with whose opinion is this mishna? It is in accordance with the opinion of Rabbi Eliezer.

§ Rav Naḥman says that Rabba bar Avuh says that Rav says: In a case where one had two pieces of fat before him, one of permitted fat and one of forbidden fat, and he ate one of them and he does not know which of them he ate, he is obligated to bring a provisional guilt offering. But if there was only one piece before him and it was uncertain if it is of forbidden fat and uncertain if it is of permitted fat, and he ate it, he is exempt.

Rav Naḥman said: What is the reason for the opinion of Rav? He holds that one is liable in the case of two pieces because the prohibition was established, i.e., there was definitely a prohibited piece before him, and nevertheless he proceeded to eat one of them. By contrast, he is exempt in the case of one uncertain piece, as the prohibition was not established.

The Gemara asks: What difference is there between the reasoning for Rav’s opinion given by Rav Naḥman, that one is liable in the case of two pieces because the prohibition was established, and the reasoning given by Rabbi Zeira, that if there is one piece it is impossible to identify its prohibition?

The Gemara answers: The difference between them is in a case where someone had two pieces of fat before him, one of forbidden fat and one of permitted fat. And a gentile came and ate the first piece, and then a Jew came and ate the second piece. According to Rava he is exempt, because at the time when the Jew ate the uncertain piece there was only one piece present, which does not fulfill the requirement of two items, as derived from the word mitzvot in the verse. According to Rabbi Zeira he is exempt because it is impossible to identify its prohibition, as both pieces are gone. But according to Rav Naḥman he is liable to bring a provisional guilt offering, as the presence of a prohibition was established, i.e., there was definitely a forbidden piece there at one point.

Rava raised an objection to Rav Naḥman from a baraita. Rabbi Eliezer says: With regard to a koy, one is obligated to bring a provisional guilt offering for eating its fat. Rav Naḥman answered: Rabbi Eliezer does not require the prohibition to be established in order for one to be obligated to bring a provisional guilt offering.

Rava raised another objection to Rav Naḥman from a baraita: If one consummates a levirate marriage with his yevama and seven months later she gives birth, there is uncertainty whether the child is nine months old and is the offspring of the first husband, or whether the child is only seven months old and is the offspring of the latter husband, and therefore he must divorce her; but the offspring is of unflawed lineage. And they are each obligated to bring a provisional guilt offering. Once again, the Gemara responds: In accordance with whose opinion is this baraita? It is in accordance with the opinion of Rabbi Eliezer.

Rava raised a final objection to Rav Naḥman from a mishna: If blood was found on his cloth, the woman and her husband are both ritually impure for seven days and they are each liable to bring a sin offering. If blood was found on her cloth immediately after intercourse, they are impure for seven days and are each liable to bring a sin offering. If it was found on her cloth after time passed, they are both impure due to uncertainty and they are exempt from bringing the sin offering. And it is taught with regard to this last case that they each is liable to bring a provisional guilt offering.

When presented with this last objection, Rav Naḥman was silent and did not reply. After Rava left he said: What is the reason I did not say to him, i.e., I should have said to him, that in accordance with whose opinion is this mishna? It is in accordance with the opinion of Rabbi Meir, who does not require the prohibition to be established in order for one to be obligated to bring a provisional guilt offering.

As it is taught in a baraita: If one slaughters an animal designated as a provisional guilt offering outside the Temple, Rabbi Meir deems him obligated to bring a provisional guilt offering and the Rabbis deem him exempt. Rabbi Meir deems him obligated to bring a provisional guilt offering despite the fact that it is possible the owner of the first provisional guilt offering never violated any transgression and therefore was never obligated to bring his provisional guilt offering. This demonstrates that according to Rabbi Meir it is not necessary for the prohibition to be established for one to be obligated to bring a provisional guilt offering.

The Gemara asks: But why did Rav Naḥman say that he could have responded to Rava’s contradiction by claiming the mishna is in accordance with the opinion of Rabbi Meir? Let him say to him that the mishna is in accordance with the opinion of Rabbi Eliezer, as was the response to the previous objections. The Gemara explains that this is what Rav Naḥman is teaching us: That the reason for the ruling of Rabbi Meir is that he holds in accordance with the opinion of Rabbi Eliezer, who says an established prohibition is not required for one to be obligated in a provisional guilt offering.

§ Rabba bar Avuh says that Rav says: If there was a piece of fat before someone and it was uncertain if it is of forbidden fat and uncertain if it is of permitted fat, and he ate it, we have arrived at the dispute between Rabbi Eliezer and the Rabbis. In a mishna on 25a, Rabbi Eliezer states that one may bring a voluntary provisional guilt offering whenever he pleases. The Rabbis disagree and maintain that a provisional guilt offering may be brought only in a case of actual uncertainty whether one performed a sin for which he would be liable to bring a sin offering.

The Gemara asks: Why did Rav specifically choose a case where one ate the item of uncertain status in order to exemplify the opinion of Rabbi Eliezer? Even if he had not eaten anything, Rabbi Eliezer would also permit him to bring a provisional guilt offering, as we learned in the mishna that Rabbi Eliezer says: A person may volunteer to bring a provisional guilt offering every day.

Rav Ashi said: Rav mentioned a case involving the consumption of an item whose status is uncertain in order to teach the ruling of Rabbi Eliezer in accordance with the opinion of Bava ben Buta, as we learned in the mishna: They said about Bava ben Buta that he would volunteer to bring a provisional guilt offering every day except for the day after Yom Kippur, as Yom Kippur atones for all uncertain sins. He said: If they would have allowed me to do so I would have brought a provisional guilt offering even on that day. But they say to him: Wait until you enter into a situation of potential uncertainty. For this reason Rav presents a scenario where an item whose status is uncertain was consumed, in order to allow for the potential uncertainty that would justify bringing a provisional guilt offering.

§ The Sages taught in a baraita: In a case where one had before him two pieces of fat, one of permitted fat and one of forbidden fat, if a Jew came and ate the first piece and then a gentile came and ate the second, the Jew is liable to bring a provisional guilt offering. And the same applies if a dog ate the second piece and the same is true if a raven ate it. But if a gentile came and ate the first piece and then a Jew came and ate the second piece, the Jew is exempt, because at the time that he ate the uncertain piece there was only one item of uncertainty. And Rabbi Yehuda HaNasi deems him obligated to bring a provisional guilt offering, as he does not maintain that two items are required for one to be obligated to bring a provisional guilt offering.

The baraita continues: If the Jew ate the first piece unwittingly and the second intentionally, he is liable to bring a provisional guilt offering for the first piece. But if he ate the first piece intentionally and the second piece unwittingly, he is exempt, because at the time that he ate the second piece, only one piece was present. Rabbi Yehuda HaNasi deems him obligated to bring an offering. If he ate both of them intentionally, he is exempt from bringing anything.

The baraita concludes: If two Jews each ate one of two items, each of them unwittingly, each of them is liable to bring a provisional guilt offering, albeit for different reasons. The first is liable to bring a provisional guilt offering in case he ate the forbidden piece. By contrast, the second one is not strictly obligated by law, as he unwittingly ate the uncertain piece when there was no other piece present. Rather, the reason he is obligated is that if you say he is exempt, you have in effect established that the first individual is obligated to bring a sin offering. One might think that the second individual is exempt because he definitely ate the permitted piece, which would mean the first one ate the forbidden piece and he must therefore bring a sin offering.

The Gemara asks: And in accordance with whose opinion is this ruling? If it is in accordance with the opinion of Rabbi Yehuda HaNasi, why does the baraita say the second individual is obligated to bring a provisional guilt offering merely as a precaution and not by law? It is certainly by law that the second is obligated to bring a provisional guilt offering, as Rabbi Yehuda HaNasi maintains that one is obligated even for an uncertainty involving a single item. If it is in accordance with the Rabbis, can it be correct that merely in order to prevent a misunderstanding and ensure that we do not establish the first one as obligated to bring a sin offering, that we would say to the second individual: Bring and slaughter a non-sacred animal in the Temple courtyard? After all, he is not obligated to bring a provisional guilt offering. Rav Ashi said in response: