But according to Levi, who said there are two sources, why do I need this woman to wait seven clean days? It should be enough for her to wait seven days after experiencing any amount of cleanliness from the conclusion of her days of impurity. After all, according to Levi, once the blood ceases to flow from her days of impurity, any blood emitted thereafter is from the source of pure blood. Consequently, even if she experiences a flow of blood during the seven clean days this should not negate her count.

The Gemara explains that this is what the baraita is saying: She requires that the blood flow should stop for any amount of time after her days of impurity, so that she will have entered her days of purity, and consequently, the next seven days will be considered for her as the seven clean days required by a zava.

The Gemara suggests: Come and hear a baraita: There are certain women with regard to whom the halakha is that if they notice an emission of menstrual blood they are deemed impure only from when they saw the blood, and one is not concerned they might have experienced the emission from an earlier time. Two such women are one who is pregnant and one who is nursing. This applies only to a pregnant woman who has been noticeably pregnant for three periods, each thirty days in length, and has not experienced bleeding during the three periods; and to a nursing woman who has been nursing for three periods, each also thirty days in length, and did not experience bleeding during that time. With regard to this the baraita teaches: The days of her pregnancy in which she saw no blood count for her toward the days of her nursing in which she saw no blood, to complete three periods, and likewise, the days of her nursing count for her toward the days of her pregnancy.

The baraita elaborates: How so? If a woman stopped experiencing bleeding for two periods during her days of pregnancy and one period during her days of nursing; or if she did not experience bleeding for two periods during her days of nursing and one period during her days of pregnancy; or if she did not experience bleeding for one and a half periods during her days of pregnancy and one and a half periods during her days of nursing, the days count for her as three periods in which she did not experience bleeding, and if she experiences bleeding she is deemed impure only from the hour that she saw the blood.

The Gemara analyzes this baraita: Granted, the baraita is clear according to Rav, who said there is one source, as it is due to that reason that the woman requires a cessation of menstrual emissions for three periods in order that she may be considered a woman whose menstrual emissions have ceased. But according to Levi, who said there are two sources, why do I need a cessation of menstrual emissions for three periods? Provided the woman’s menstrual emissions cease for any amount of time at the completion of her days of impurity, it should be enough, as any blood she may emit thereafter is pure and should not negate her count of three periods.

The Gemara explains that this is what the baraita is saying: She requires that the blood flow should stop for any amount of time at the conclusion of her days of impurity, in order that her days of purity will be counted for her as part of the three periods, even if she experiences bleeding during her days of purity.

The Gemara suggests: Come and hear a baraita: And although Shammai and Hillel disagree with regard to all women who experience bleeding (see 2a), as Shammai maintains they are impure only from when they saw the blood while Hillel holds that they assume ritual impurity status retroactively from the last time they examined themselves and were found to be pure, they agree with regard to a woman who sees blood after seeing blood during her days of purity, that it is sufficient for her to be considered impure from the hour of her seeing the blood.

The Gemara analyzes the baraita: Granted, the baraita is clear according to Levi, who said there are two sources, as it is due to that reason that it is sufficient for her to be considered impure from the hour of her seeing the blood. In other words, although she experienced bleeding during her days of purity, until this emission she was still considered a woman whose menstrual emissions have ceased. But according to Rav, who said there is one source, if this woman experienced bleeding during her days of purity, she cannot be considered a woman whose menstrual emissions have ceased. If so, why is it sufficient for her to be considered impure from the hour of her seeing the blood? She should be considered impure retroactively for a twenty-four-hour period, like all other women.

The Gemara responds: The baraita is referring to a case where there is no time between the conclusion of her days of purity and the subsequent emission of blood. In such a situation, she cannot be considered impure retroactively for a twenty-four-hour period, as the previous twenty-four hours are part of her days of purity.

The Gemara raises a difficulty: But still, why is she impure only from when she sees the blood? She should be considered impure from examination to examination, i.e., from the last time she examined herself and found that she was pure. The Gemara responds: Since there is no possibility of her being impure retroactively for a twenty-four-hour period, with regard to impurity from examination to examination as well, the Sages did not decree impurity with regard to her.

The Gemara further suggests: Come and hear a baraita: With regard to a woman who gives birth as a zava, who counted seven clean days after the conclusion of her days of impurity but did not yet immerse, and subsequently saw blood, Beit Shammai follow their opinion with regard to any woman who gave birth and concluded her days of impurity but did not yet immerse, and Beit Hillel likewise follow their opinion. In other words, according to Beit Shammai her blood imparts impurity only while moist, whereas according to Beit Hillel it imparts impurity whether it is moist or dry.

The Gemara analyzes the baraita: Granted, the baraita is clear according to Rav, who said there is one source, as it is due to that reason Beit Hillel maintain that the blood imparts impurity whether it is moist or dry. In other words, as she has not yet immersed, the Torah does not deem pure her menstrual emissions. But according to Levi, who said there are two sources, any blood she may emit after counting seven clean days must have come from the source of pure blood. If so, why does it impart impurity whether it is moist or dry?

The Gemara explains that Levi could say to you: I say my opinion in accordance with the opinion of the tanna of the baraita cited above, that Shammai and Hillel agree that with regard to a woman who experiences bleeding after experiencing bleeding during her days of purity, it is sufficient for her to be considered impure from the hour that she saw the blood. That baraita apparently indicates that there are in fact two sources.

And if you wish, say instead that this baraita is referring to a woman who continuously discharges menstrual blood from within her days of impurity into her days of purity. Accordingly, the blood she sees during her days of purity is still from the source of impure blood. The Gemara objects: But the baraita teaches that the woman counted seven clean days.

The Gemara explains: Here we are dealing with a woman who gave birth to a female as a zava, and therefore her days of impurity are two weeks in length. And this is a case where in the first week her menstrual emissions ceased, and in the latter week her menstrual emissions did not cease, and they continued until her days of purity. And the tanna of this baraita holds: The days of her birth, i.e., the days of impurity, in which she does not see blood, count for her toward the counting of her ziva. Accordingly, although she is considered to have counted seven clean days, the blood emitted during her days of purity is from the source of impure blood.

§ With regard to the dispute between Rav and Levi, Ravina said to Rav Ashi: Rav Shemen from Sikhra said to us: Mar Zutra happened to come to our locale, and he taught that the halakha is in accordance with the opinion of Rav as a stringency, and the halakha is in accordance with the opinion of Levi as a stringency. In other words, if a woman continuously discharges menstrual blood from within her days of purity until sometime after the conclusion of her days of purity, the blood emitted after her days of purity is impure, in accordance with the opinion of Rav. By contrast, if she continuously discharges menstrual blood from within her days of impurity into her days of purity, the blood emitted during her days of purity is impure, in accordance with the opinion of Levi.

Rav Ashi said: The halakha is in accordance with the opinion of Rav, whether as a leniency or as a stringency. Likewise, Mareimar taught: The halakha is in accordance with the opinion of Rav, whether as a leniency or as a stringency. The Gemara concludes: And the halakha is in accordance with the opinion of Rav, whether as a leniency or as a stringency.