It is the opinion of Beit Shammai, who say that there is only one source for the two types of blood (see 35b). The Gemara asks: But can it be that the tanna taught us an unattributed mishna, which is generally accepted as the halakha, in accordance with the opinion of Beit Shammai, whose opinion is usually not accepted as halakha? The Gemara answers: It is a case where the mishna first records an unattributed opinion and afterward it records a dispute with regard to the same matter. And there is a principle that any time the mishna first records an unattributed opinion and afterward it records that the ruling is subject to a dispute, then the halakha is not necessarily in accordance with the unattributed opinion.

And if you wish, say instead: Does the mishna teach: A woman is anticipating observing the period of the blood of purity? Rather, it teaches: Who is observing the period of the blood of purity. The Gemara asks: If the mishna is referring to a woman who is already observing the period of the blood of purity, what is the purpose of stating that she is exempt from performing examinations? Isn’t this obvious? The Gemara answers: Lest you say that she should examine herself, as perhaps she will find that she established a fixed menstrual cycle through blood found on her examination cloths, the mishna teaches us that a woman does not establish a cycle from sightings of blood that came from a pure source that transfers to the period when she sees blood from an impure source.

The Gemara raises a difficulty with regard to this answer: This answer works out well according to Levi, who said that there are two distinct sources, one for blood after birth and one for blood of purity; one can understand that she does not establish a cycle with regard to blood from one source, from a sighting of blood from a different source. But according to Rav, who said that blood after birth and blood of purity both come from one source, she should be required to examine herself during the period of the blood of purity, as perhaps she established a fixed menstrual cycle. The Gemara answers: Even so, i.e., that both types of blood come from the same source, nevertheless a woman does not establish a cycle from her days of purity that transfers to her days of impurity.

§ The mishna teaches: And even a woman with a fixed menstrual cycle engages in intercourse while using examination cloths to ascertain whether her menstrual flow began, except for a woman after childbirth who is observing the period of the blood of purity, and a virgin whose blood is ritually pure for four days after engaging in intercourse for the first time. In this connection, the Gemara notes that we learned in a mishna there (64b): With regard to a young girl whose time to see the flow of menstrual blood has not arrived, as she has not yet reached puberty, and she married, Beit Shammai say: The Sages give her four nights after intercourse during which the blood is attributed to her torn hymen and she is ritually pure. Thereafter, any blood is menstrual blood and she is impure. And Beit Hillel say: The blood is attributed to the torn hymen until the wound heals.

With regard to Beit Hillel’s statement, Rav Giddel says that Shmuel says: They taught this only in a case where she does not stop seeing blood due to intercourse. In other words, every time she engages in intercourse she experiences bleeding. In that case, even if she saw blood not due to intercourse, Beit Hillel still attribute the blood to the torn hymen. But if she stops seeing blood due to intercourse, and then she subsequently saw blood on another occasion, that blood renders her impure.

He continues: Similarly, if one night passed without them engaging in intercourse and she subsequently saw blood without connection to intercourse, this indicates that the blood is no longer from her torn hymen and therefore she is deemed impure. Likewise, if the appearance of her blood had changed since her initial blood from her torn hymen, she is impure. Rabbi Yona raises an objection to this last halakha from the mishna: And a virgin whose blood is ritually pure is not required to examine herself when she engages in intercourse. Why not? She should engage in intercourse while using examination cloths, as perhaps she will find that the appearance of her blood has changed, which would mean that her blood is no longer ritually pure blood from her torn hymen.

Rava says: Say the first clause: All women must engage in intercourse while using examination cloths, except for a menstruating woman whose impure status is certain and a woman after childbirth who is observing the period of the blood of purity. It can be inferred from here that these two exceptions are not required for women to examine themselves, but a virgin whose blood is pure is required to perform an examination. This ruling apparently supports Shmuel’s opinion that examination is required to determine if there is a change in the appearance of her blood. But if so, then the two clauses of the mishna are difficult, as they contradict each other.

The Gemara explains: Here, in the latter clause that indicates that a virgin requires no examination, it is referring to a case where she had engaged in intercourse. In such a situation an examination would be inconclusive, as even if the appearance of her blood had changed, one can say that it was because the man’s organ soiled it, i.e., perhaps the intercourse caused the change of appearance in her blood. By contrast, there, in the first clause, it is referring to a case where she had not engaged in intercourse, and therefore she is required to perform an examination to determine if there was a change in appearance in her blood, as any difference in appearance would indicate a change from pure blood to impure blood.

The Gemara notes that this halakha is also taught in a baraita. With regard to the opinion of Beit Hillel that blood is attributed to the torn hymen until the wound heals, the baraita asks: In what case is this statement said? In a case where she does not stop seeing blood due to intercourse, i.e., every time she engages in intercourse she experiences bleeding. If so, even when she sees blood not due to intercourse, it is deemed pure.

But if she stopped seeing blood due to intercourse, and she subsequently sees blood at a different time, that sighting renders her impure. Similarly, if one night passed without her engaging in intercourse and then she saw blood without connection to intercourse, she is deemed impure. Furthermore, if she sees blood and the appearance of her blood had changed from her initial blood from her torn hymen, she is impure.

§ The mishna teaches: And she is required to examine herself twice each day, in the morning and at twilight. Rav Yehuda says that Shmuel says: The mishna taught this halakha only with regard to touching ritually pure items. But with regard to her husband, she is permitted to him without any requirement to perform examinations. The Gemara asks: Isn’t this obvious, as we learn in the mishna that she must examine herself twice a day, and the first time is in the morning? This indicates that the mishna is concerned about the status of ritually pure items that she will handle during the day, but not about intercourse with her husband, as a couple usually engages in relations at night rather than during the day.

The Gemara answers: Rather, if the statement of Rav Yehuda citing Shmuel was stated, it was stated with regard to the latter clause of the mishna: And she is also required to examine herself at a time that she is about to engage in intercourse with her husband. Rav Yehuda says that Shmuel says: The mishna taught this halakha only with regard to a woman who is engaged in handling pure items. She alone is required to examine herself before intercourse. The reason is that since she is required to perform an examination in preparation for handling pure items, she also requires an examination in preparation for intercourse with her husband. But with regard to a woman who is not engaged in handling pure items, she is not required to perform an examination in preparation for intercourse with her husband.

The Gemara asks: What is Rav Yehuda teaching us? We already learn this from the mishna (15a): All women have the presumptive status of purity to their husbands, and therefore the husband does not need to ascertain whether she is ritually pure before engaging in intercourse. The Gemara answers: If this halakha is learned from the mishna alone, I would say that this statement applies only to a woman who has a fixed menstrual cycle. But in the case of a woman who does not have a fixed menstrual cycle, she is required to perform an examination before intercourse. Consequently, Rav Yehuda teaches us that even a woman who does not have a fixed menstrual cycle is not required to perform an examination before intercourse, unless she handles pure items.

The Gemara asks: But aren’t we are dealing in the mishna with a case of a woman who has a fixed menstrual cycle? The Gemara answers: The mishna is dealing both with a case where she has a fixed menstrual cycle and with a case where she does not have a fixed menstrual cycle. And this is what the mishna teaches us: That even though she has a fixed menstrual cycle, and therefore one might think that she is exempt from examination, nevertheless if she handles pure items, since she is required to perform an examination in preparation for handling those pure items, she is also required to perform an examination in preparation for intercourse with her husband.

The Gemara asks: But didn’t Shmuel already state this halakha on another occasion? As Rabbi Zeira said that Rabbi Abba bar Yirmeya says that Shmuel says: With regard to a woman who does not have a fixed menstrual cycle, it is forbidden for her to engage in intercourse with her husband until she examines herself and determines that she is pure. And we interpreted this halakha as referring to a case where she is engaged in handling pure items. The Gemara answers: Shmuel did not in fact issue two statements; rather, one was stated by inference from the other. In other words, Shmuel said one of these statements explicitly; the other was reported by his students in his name based on an inference from what he had said.

The Gemara adds: This is also taught in a baraita: In what case is this statement, that a woman requires an examination, said? It is said with regard to a woman who is preparing for handling pure items. But with regard to engaging in intercourse with her husband, she is permitted to do so without performing an examination. The baraita qualifies this ruling: And in what case is this statement, that she is not required to perform an examination, said? It is said when her husband traveled and left her with the presumptive status of ritual purity. If so, upon his return she does not need to perform an examination before they engage in intercourse. But if he left her with the presumptive status of ritual impurity, she remains forever in her status of impurity, until she says to him: I am ritually pure.