2,046. A Niddah

Hilchos Issurei Biah 4:1

A menstruous woman (i.e., a niddah) is like any other prohibited relationship. A man who inserts his tip into her “regularly” or “irregularly” is liable to kareis. This applies even to a minor three years of age, the same as with other prohibited relationships. This is because a woman can become a niddah even on the day of her birth, and a girl ten days old because of zivah (a certain type of emission). This has been communicated to us through our oral tradition. There’s no difference between an adult and a minor when it comes to the ritual impurities of niddah and zivah.

Hilchos Issurei Biah 4:2

Prohibited relations with a niddah apply for seven days even if blood was only seen on the first day. The same is true if one has relations with a woman who gave birth to a boy for seven days, with a woman who gave birth to a girl for 14 days, or with a zavah until the time she bleeds and counts (seven clean days). Whether a Canaanite servant woman or freed, all of these are subject to kareis, as follows. Regarding a niddah, Leviticus 15:19 says, “She will be in her impurity for seven days.” Regarding a zavah, verse 25 says, “All the days of her flow will be like the days of her impurity.” Regarding a woman who gave birth to a boy, Leviticus 12:2 says, “She will be unclean like the days of her niddah affliction.” Regarding a woman who gave birth to a girl, verse 12:5 says, “She will be impure for two weeks like her niddah state.”