Niddah 10:1-2

Niddah 10:1

If a girl hasn’t yet reached the age to menstruate and she marries, Beis Shammai say she is given four nights (in which we assume that any blood seen is hymeneal rather than menstrual); Beis Hillel say she’s given until the wound heals. If she has reached the age (but hasn’t yet menstruated), Beis Shammai say she is given one night and Beis Hillel say she is given four nights, until Saturday night (virgins typically married on Wednesdays). If she menstruated while still living in her father’s house (i.e., before marriage), Beis Shammai say she is given just the first act of marital intimacy, while Beis Hillel say she is given the entire night.

Niddah 10:2

Let’s say that a niddah checked herself on the seventh day (after her period began) in the morning and found herself clean but at twilight she neglected to perform a separation examination. A few days later, she checks and finds herself unclean. In such a case, she is presumed to have been clean in the interim. Let’s say that she checked herself on the seventh day in the morning and found herself unclean and neglected to perform a separation examination at twilight. If she later checks and finds herself clean, she is presumed to have been unclean in the interim. She (the woman in the first scenario) conveys ritual impurity retroactive either for 24 hours or to her last examination; if she has a fixed time for her period, that is sufficient. Rabbi Yehuda says that if a woman didn’t perform a separation examination after the afternoon of the seventh day, she is presumed to be unclean. The Sages say that even if she examined herself on the second day after her period began and found herself clean, then she neglected to perform a separation examination, and she later checked and found herself unclean, she is presumed to have been clean in the interim.