Study Niddah folio 64B with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
And she is prohibited on the 20th day, because it is the manner of women that their blood flow comes at its usual time.
Mishnah: Women, with regard to the blood that flows when their hymens are ruptured, are like grapevines: There is a vine that produces wine that is red, and there is a vine that produces wine that is black; and there is a vine that produces wine in abundance, and there is a vine that produces only
Talmud: With regard to the term durkati, the Talmud explains that this means truncated generation [dor katua]. As R' Ḥiyya teaches: Just as leaven is good for dough, so too, blood is good for a woman. It was likewise taught in the name of R' Meir: Any woman whose blood is plentiful, her children
Mishnah: In the case of a young girl whose time to see a menstrual flow, i.e., the age of puberty, has not yet arrived, and she married and had sex and her hymen was torn, Beit Shammai say: The rabbis give her 4 nights after sex during which the blood is attributed to the torn hymen and she remain