מידי הוא טעמא אלא לרבי יוחנן האמר ליה רבי יוחנן לתנא תני בטלו חייב ולא בטלו פטור
The Gemara answers: The only reason Rava stated his explanation, that all his days he is obligated to arise and remarry her and that is why the rapist is not flogged even though it is a prohibition preceded by a positive mitzva, is to explain the opinion of Rabbi Yoḥanan, who said that for any prohibition that has a positive mitzva which preceded it, everyone agrees that one is flogged for its violation. Didn’t Rabbi Yoḥanan say to the tanna who would recite the mishnayot and baraitot in the study hall: Teach that if he nullified the mitzva, he is liable to receive lashes, and if he did not nullify the mitzva, he is exempt from lashes? According to Rabbi Yoḥanan, it works out well.
דתני תנא קמיה דרבי יוחנן כל מצות לא תעשה שיש בה קום עשה קיים עשה שבה פטור ביטל עשה שבה חייב
What is the dispute to which the Gemara is alluding? The tanna taught a baraita before Rabbi Yoḥanan: With regard to any prohibition that entails a command to arise and perform a mitzva, if he fulfilled the positive mitzva that is entailed therein, he is exempt from lashes, and if he nullified the positive mitzva that is entailed therein, he is liable to receive lashes.
א"ל מאי קא אמרת קיים פטור לא קיים חייב ביטל חייב לא ביטל פטור תני ביטלו ולא ביטלו ורבי שמעון בן לקיש אומר קיימו ולא קיימו
Rabbi Yoḥanan said to the tanna: What is it that you are saying? The baraita that you recited is self-contradictory, as based on the first clause: If he fulfilled the mitzva he is exempt, apparently, if he did not fulfill the mitzva he is liable. Yet based on the latter clause: If he nullified the mitzva, he is liable, apparently, if he did not nullify the mitzva he is exempt, even though he failed to fulfill the mitzva. Rather, teach: If he nullified the mitzva, he is liable to receive lashes, and if he did not nullify the mitzva, he is exempt from lashes. And Rabbi Shimon ben Lakish says: The formulation of the baraita must be consistent; therefore, teach: If he fulfilled the mitzva, he is exempt, and if he did not fulfill the mitzva he is liable.
במאי קא מיפלגי בהתראת ספק קא מיפלגי מר סבר התראת ספק שמה התראה
The Gemara inquires: With regard to what matter do they disagree? They disagree with regard to uncertain forewarning, i.e., forewarning concerning a transgression with regard to which it will not be clarified whether or not his action will render him liable to receive lashes. One Sage, Rabbi Yoḥanan, holds: Uncertain forewarning is characterized as forewarning; therefore, even if it is unclear whether the action that the transgressor is about to perform will render him liable to receive lashes, he can be forewarned, and if he violates the prohibition in a manner that will render him liable, he is flogged.
ומר סבר התראת ספק לא שמה התראה
And one Sage, Reish Lakish, holds: Uncertain forewarning is not characterized as forewarning. According to Rabbi Yoḥanan, the rapist is forewarned when he is about to divorce his wife, even though there is uncertainty whether he will nullify the mitzva. If he nullifies the mitzva, e.g., if he vows that deriving benefit from his ex-wife is forbidden to him, thereby ensuring that he cannot remarry her, he is flogged. Reish Lakish holds that if one’s liability to receive lashes was dependent upon the nullification of the mitzva, the rapist would never be flogged, as in that case the forewarning would of necessity be uncertain. Therefore, he explains that the criterion for determining whether one is flogged is whether he fulfilled the mitzva immediately. Violating the prohibition renders him liable to receive lashes; he may then choose to be flogged or to fulfill the mitzva. Therefore, when he is forewarned that he will be flogged if he divorces her, it is not uncertain forewarning.
ואזדו לטעמייהו דאיתמר שבועה שאוכל ככר זה היום ועבר היום ולא אכלה רבי יוחנן ור"ל דאמרי תרוייהו אינו לוקה רבי יוחנן אומר אינו לוקה
And they follow their standard lines of reasoning, as it was stated that Rabbi Yoḥanan and Reish Lakish disagreed in a case where one said: On my oath I will eat this loaf today, and the day passed and he did not eat it. Rabbi Yoḥanan and Reish Lakish both say: He is not flogged for taking a false oath. They disagree with regard to the reason that he is not flogged. Rabbi Yoḥanan says: He is not flogged,