actually misguided? Since they are in doubt as to their status, would it not be more accurate to say that they are mistaken? The Gemara answers: Rather, this is how one should teach the statement of Rabbi Yehoshua in the mishna: Instead of making provisions to remedy the uncertainties of the mistaken, come and remedy the uncertainties of the competent women.

As it is taught in a baraita with regard to these competent women: What is the halakha in the case of a woman who consistently has the following pattern for each pair of days: One day she is impure, i.e., she experiences bleeding, and one day she is pure, she does not experience bleeding? In what manner is it permitted for her to engage in intercourse with her husband? She may engage in intercourse with her husband on the eighth day from the first time that she experienced bleeding and its accompanying night. At that time she is pure from her menstruation, as she immersed and purified herself on the night of the seventh day. It is permitted for her to engage in intercourse during the eighth day and the following night, as she will not experience bleeding until the ninth day.

In addition, she may engage in intercourse four nights out of the cycle of eighteen days, which consist of the seven menstrual days and the eleven days of the flow of the zava. This woman will never become a greater zava, as she does not emit blood on consecutive days. Since she must observe a day of purity during the eleven days of ziva each time she experiences bleeding, she may engage in intercourse with her husband on the night following the tenth, twelfth, fourteen, and sixteenth days. The night after the eighteenth day is considered part of the next cycle of menstruation and ziva. But if she sees blood in the evening, she may engage in intercourse with her husband only on the eighth night and its day. During the eleven days of ziva she either experiences bleeding at night or is observing a day of purity for the blood she had emitted earlier.

If in every set of four days, two days she is impure, i.e., experiences bleeding, and two days she is pure, she may engage in intercourse with her husband on the eighth day, in the day or at night, and also on the twelfth day, after observing the eleventh as a day of purity for the sightings of the ninth and tenth days, and by a similar calculation on the sixteenth day and on the twentieth day, as she has not yet seen the blood of menstruation in this new cycle.

The Gemara objects: And let her also engage in intercourse with her husband on the nineteenth day, as the eleven days of the flow of the zava have already passed at the end of the eighteenth day, and she is no longer required to observe a clean day for each day she experiences a discharge. Rav Sheshet says: That is to say that when we learned in a mishna (72a) that a husband who could not wait for the conclusion of the day after the last day of ziva before engaging in intercourse is a glutton, it means that it is actually prohibited for them to engage in intercourse.

Rav Ashi says: In fact, it is not prohibited for a woman to engage in intercourse with her husband on the day after the end of the days of the flow of the zava even by rabbinic decree, as it is already the beginning of her menstrual days, and she is no longer required to observe a clean day for each day she experiences a discharge. But although there is no requirement to observe a clean day for the eleventh day of ziva, which is the eighteenth day of the full cycle, in any event there is a requirement to observe a clean day for the tenth day, i.e., the seventeenth of the entire cycle. Since she did not observe a clean day on the eighteenth day, as she saw blood on that day as well, she must observe the nineteenth day in purity.

If out of every set of six days, three days she is impure, and three days she is pure, she may engage in intercourse with her husband during two of the days, and thereafter she may never again engage in intercourse with him. The eighth and ninth days, which are the first days of the flow of ziva, are the second and third of the three days on which she experiences bleeding. Therefore, she can immerse and purify herself on the night of the eleventh, and engage in intercourse with her husband on the eleventh and twelfth days. These are the only two days on which she is permitted to engage in intercourse with her husband, as afterward she will experience bleeding for three days during the days of the flow of the zava, and is thereby rendered a greater zava. Accordingly, she requires seven clean days to become pure again, which she will never attain, as she never has more than three clean days.

If out of every set of eight days, four days she is impure, and four days she is pure, she may engage in intercourse with her husband during one of the days, the eighth, after her purification for menstruation, as it is the last of her first set of four days without blood, and thereafter she may never again engage in intercourse with him, as she will be rendered a greater zava by experiencing bleeding on the next three days.

If out of every set of ten days, five days she is impure, and five days she is pure, she may engage in intercourse with her husband during three of the days, i.e., the eighth, ninth, and tenth, as she has completed her menstruation period and has not yet emitted the blood of ziva, and thereafter she may never again engage in intercourse with him. Similarly, if out of every set of twelve days, six days she is impure, and six days she is pure, she may engage in intercourse with her husband during five of the days, i.e., the eighth to the twelfth, and thereafter she may never again engage in intercourse with him.

If out of every set of fourteen days, seven days she is impure, and seven days she is pure, she may engage in intercourse with her husband during a quarter of the days of her life, i.e., seven out of every twenty-eight days. In the first seven days she is a menstruating woman, but during the next seven days she is pure. In the third set of seven days, when she again experiences bleeding, she becomes a zava, which means that in her last seven days, which are without blood, she counts the clean days for her ziva, after which this cycle of twenty-eight days begins afresh.

If out of every set of sixteen days, eight days she is impure, and eight days she is pure, she may engage in intercourse with her husband fifteen days out of every forty-eight days. The first eight days during which she experiences bleeding are the seven days of menstruation and one day of ziva, which renders her a lesser zava. Therefore, she must observe one clean day, after which she is pure for seven days. The first two days of the third set of eight are her last days of ziva, and the bleeding she experiences renders her again a lesser zava, while the next six are during her days of menstruation. Then she starts her fourth set of eight days, which are without blood. The first of these completes her days of menstruation, after which she may engage in intercourse for the subsequent seven days. During the fifth set of eight days she experiences bleeding, rendering her a greater zava. She counts her clean days in the sixth set, leaving her one day of purity, after which the cycle of forty-eight days starts again.

The Gemara objects: But the days during which she is permitted are actually only fourteen, not fifteen. This objection is based on the assumption that a woman cannot count her clean days for ziva during days that are fit for menstruation. Consequently, the last four days of the fifth cycle are actually part of her days of menstruation, as her eleven days of ziva ended after the fourth day of that cycle. If so, the sixth set of eight days consists of three menstrual days followed by five days of ziva. Although she is not a menstruating woman in those three days, as she did not previously count seven clean days, they still do not count for her seven clean days of ziva, since they are fit to be menstrual days. She can start counting her seven clean days only on day forty-four, but on day forty-nine, before the seven clean days are finished, she will again experience bleeding. Therefore, it should not be permitted for her to engage in intercourse with her husband on the forty-eighth night.

Rav Adda bar Yitzḥak says that this premise should be rejected: That is to say that her menstrual days on which she does not actually see blood do count toward her counting of her seven clean days of ziva. In other words, she begins counting the seven clean days during these menstrual days. As a dilemma was raised before the Sages with regard to this issue: