Abba Shaul says: Even if he did not cut his hair before the pilgrimage Festival, it is permitted for him to cut his hair after the pilgrimage Festival. His reasoning is that just as the mitzva of three voids the rabbinic decree of seven, as was taught before; so the mitzva of seven voids the rabbinic decree of thirty. Since he completed the observance of the seven days of mourning before the Festival, he need not observe the thirty days of mourning.

The Gemara asks: What is the rationale of Abba Shaul for his opinion that if he observed seven days of mourning before the Festival commenced the thirty-day mourning period is voided? Isn’t it because he holds that the seventh day counts for here and there, i.e., the seventh day is considered both the end of the seven days and the start of the thirty days of mourning, so he had already begun observing his thirty days of mourning before the start of the Festival? This ruling may be the basis for the ruling of Rav. The Gemara rejects this: This does not support Rav, since perhaps Abba Shaul was saying his ruling that the same day counts for both here and there only with regard to the mourning of seven days, which is by rabbinic law, but with regard to a nazirite, whose obligation is by Torah law, he would not say so.

Rather, Rav spoke in accordance with the opinion of Rabbi Yosei, as it is taught in a baraita that Rabbi Yosei says: A woman who observes a clean day for each day she experiences a discharge is a woman who discharges blood for one or two days at a time when she does not expect her menstrual period. The case under discussion is one where she experienced a discharge for one day and they slaughtered a Paschal offering and sprinkled the blood for her on her second day, after she immersed in a ritual bath. At that point, it is unclear whether she will remain clean of discharges for the remainder of the day, in which case she is retroactively pure from the time she immersed and may eat the Paschal offering at night, or whether she will experience a discharge of blood during the day, in which case her immersion is retroactively invalid and she was impure the entire time.

And after that, she saw blood, thereby retroactively clarifying that at the time the Paschal offering was slaughtered she was unfit to partake of it. The halakha is that she may not eat from the Paschal lamb due to her ritual impurity, but she is exempt from observing the second Pesaḥ, which is observed by those who did not sacrifice the Paschal offering on the first Pesaḥ. The reason is that since she was pure when they slaughtered the Paschal offering on her behalf, she has fulfilled the obligation of the offering, despite the fact that she became impure and was unable to eat the offering.

The Gemara clarifies this: What is the rationale of Rabbi Yosei for his opinion that she is exempt from observing the second Pesaḥ? Isn’t it because he holds that the legal status of part of the day is like that of an entire day? Since she was pure for part of the day, it is considered as though she was pure the entire day. The Gemara rejects this: From where do you know that this is the rationale? Perhaps it is because Rabbi Yosei holds that one becomes impure from now and onward. He holds that the impurity of a zava starts only from the moment she had a discharge of blood, but she is ritually pure up to that point, so she was ritually pure when they slaughtered the offering for her.

The Gemara questions this explanation: And does Rabbi Yosei hold in accordance with this ruling that she is impure only from that moment onward?

But isn’t it taught in a baraita that Rabbi Yosei says: With regard to a man who experiences a gonorrhea-like discharge [zav] who has had two sightings of discharge, for whom they slaughtered a Paschal offering and sprinkled its blood on the seventh, and final, day of impurity, and similarly, with regard to a woman who observes a clean day for a day, for whom they slaughtered a Paschal offering and sprinkled its blood, and afterward they saw their respective discharges, although they render objects designed for lying and sitting impure retroactively, they are exempt from observing the second Pesaḥ. This is proof that Rabbi Yosei holds that their ritual impurity applies retroactively, rather than from the moment of discharge onward. It must be that the reason why they are nevertheless exempt from observing the second Pesaḥ is that part of the day is like the entire day, and the part of the day before they became impure, during which the blood of the Paschal offering was sprinkled for them, is considered a whole clean day.

The Gemara responds to this attempted proof: What is the meaning of Rabbi Yosei’s statement that the ritual impurity applies retroactively? It means that the ritual impurity applies retroactively by rabbinic law. However, by Torah law, the zav or zava is impure only from the time of the new sighting and onward. The Gemara adds: So too, it is reasonable that this is Rabbi Yosei’s opinion, as, if it enters your mind that they become ritually impure retroactively by Torah law, why are they exempt from observing the second Pesaḥ if by Torah law they were impure at the time the offering was slaughtered?

The Gemara responds: This is no proof, since actually, I could say to you that this retroactive impurity is by Torah law, and the reason they are exempt from observing the second Pesaḥ is that the Sages permitted impurity of the deep of ziva. The halakha is that in the case of a Paschal offering, an unknown impurity of the dead, called the impurity of the deep, is permitted. In a case where one brought his offering and later became aware that he had contracted impurity from a corpse, if this source of impurity was unknown to everyone, he is not required to observe the second Pesaḥ. The Gemara suggests that Rabbi Yosei may hold that the same halakha applies to the impurity of a zava as well: Since the owner of the offering was pure when it was brought and could not have known that she would become impure due to discharge later that day, it is similarly considered an impurity of the deep, and she has therefore fulfilled her obligation.

§ The Gemara points out: And even Rabbi Oshaya holds that, according to Rabbi Yosei, the fact that a zav renders objects designed for sitting or lying impure retroactively is only by rabbinic law in this circumstance. As it is taught in a baraita that Rabbi Oshaya says: In a case of one who sees gonorrhea-like discharge on his seventh clean day, this negates the clean days that preceded it and starts his seven days anew. And Rabbi Yoḥanan said to him that it should negate only its own day, i.e., he should require only one additional clean day.

The Gemara expresses surprise: Whichever way you look at Rabbi Yoḥanan’s statement, it is difficult. If this discharge negates clean days just as the case of a zav who had a discharge during his seven days, it should negate all his clean days, not only the last one. If it does not negate clean days, since it is not considered a discharge within his seven days but rather, as the first sighting of a new ziva, it should not negate any of it, and not even its own day. What, then, is the logic of Rabbi Yoḥanan’s ruling that it negates a single day? Rather, say instead that Rabbi Yoḥanan said as follows: It does not negate at all, and not even its own day, since this discharge is considered to be the first of a new series.