Nidá / oná bénonit

Des femmes à menstruation régulière et de celles à menstruation irrégulière.
Lorsqu’une femme a ses époques de façon irrégulière, elle doit prendre une précaution supplémentaire à la fin de chaque mois. Lorsqu’elle a ses époques de façon régulière, par exemple le 20 ou le 25 de chaque mois, elle n’a à prendre sa précaution qu’un peu avant l’époque prévue.

MISHNA:All women have the presumptive status of purity for their husbands, and therefore one is not required to ascertain whether his wife is ritually pure before engaging in intercourse with her. Even with regard to husbands returning from a journey, if their wives were ritually pure when they left, their wives have the presumptive status of purity for them.

The Gemara notes that in this regard, Reish Lakish says in the name of Rabbi Yehuda Nesia: And this halakha that the wife of a husband returning from a journey has a presumptive status of purity is applicable only in a case where the husband came and found that his wife was within the days of her projected period, i.e., within thirty days of her previous menstruation. In this case he may assume that she has not yet experienced a new period, and therefore he may rely on her presumptive status of purity. But if he arrived after thirty days had elapsed from her previous menstruation, it is assumed that she experienced menstruation at the usual time and therefore it is not permitted for him to engage in intercourse with her unless she examined herself and found herself pure.

§ With regard to the presumptive status of purity of wives, Rav Huna says: The Sages taught this halakhaonly in the case of a woman who does not have a fixed menstrual cycle. But with regard to a woman who does have a fixed menstrual cycle, it is prohibited for her husband to engage in intercourse with her.

...

§ The mishna teaches: Who is the woman characterized as an elderly woman in this context? It is any woman for whom three typical menstrual cycles of thirty days passed at a stage of her life close to her old age, during which she saw no menstrual blood. The Gemara asks: What is considered close to old age? Rav Yehuda says: Any woman about whom her friends say that she is an elderly woman. And Rabbi Shimon says:

It is any woman who is old enough that people call her: Mother [Imma], Mother, and she is not embarrassed. Rabbi Zeira and Rabbi Shmuel bar Rav Yitzḥak disagree with regard to this matter. One says that the definition is any woman who does not take offense about being called: Mother, Mother. And the other one says that it is any woman who is not embarrassed by this. The Gemara asks: What is the difference between their definitions? The Gemara answers: The practical difference between them is in a case where a woman is embarrassed but she does not take offense when called: Mother.

The Gemara asks: And how long is a typical menstrual cycle? Reish Lakish says in the name of Rabbi Yehuda Nesia: The average menstrual cycle is thirty days long. And Rava says that Rav Ḥisda says: It is twenty days. The Gemara notes: And they do not disagree. One Sage, Rav Yehuda Nesia, counts all the days of her cycle, including the days of impurity and days of purity. And the other Sage, Rav Ḥisda, does not count the days of impurity, i.e., the seven days of impurity of a menstruating woman and the three days of the sighting of ziva.

Whenever a woman has a veset, her husband can assume that she is [ritually pure and] permitted until she tells him "I am impure" or she is established as a niddah in her neighborhood.
If a woman's husband went overseas and left her ritually pure, when he comes he does not have to ask her [concerning her state]. Even if he finds her asleep, he may enter into relations with her as long as it is not the time when she is expected to menstruate. He need not suspect that perhaps she is a niddah. If he left her a niddah, she is forbidden to him until she tells him: "I am ritually pure."

...