Study Niddah folio 5A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
And as for the ruling of the baraita, that a woman who discovers menstrual blood not at her fixed time for menstruation is impure retroactively, this is a halakha with which everyone agrees.
The Talmud raises a difficulty: But let us interpret the Mishnah in the opposite manner. Why interpret the Mishnah in accordance with the opinion of R' Dosa and the baraita in accordance with everyone, when we can give precedence to the Mishnah, which is more authoritative, by interpreting it in acc
The Talmud answers: Since there is a way to interpret it as a leniency, i.e., that all agree that blood discovered at the fixed time of menstruation renders items impure only from that point onward, and it can also be interpreted in a manner that leads to a stringency, i.e., everyone agrees that b
§ It is taught in the baraita: If a woman who has a fixed menstrual cycle finds a blood stain, her blood stain is retroactively impure. The reason is that if she sees a flow of menstrual blood not at the fixed time of her menstrual cycle, it renders her ritually impure retroactively for a twenty-fo
It can be inferred from here that in the case of those other women, e.g., a pregnant or elderly woman, with regard to whom the rabbis stated: Their time is sufficient and their menstrual flow never causes retroactive impurity, the same halakha applies to their blood stains as to their sighting of t