1,065. Hilchos Niddah

152:17 Rav Berona said in the name of Rav that if one sleeps in the room of a man and his wife, then the verse "the women of My people you cast from the houses of their pleasure" (Micah 2:9) applies to him because his presence prevents their intimacy. Rav Yosef added that this is the case even when the wife is ritually unclean.

153:1 A woman is rendered a niddah by even the smallest drop of uterine blood, whether it's the usual time for her period or not. Even if some accident caused it to occur, if it's uterine blood, she becomes a niddah until she counts seven clean days (i.e., without bleeding) and immerses in a mikvah. Anyone who has sexual relations with a woman in a state of niddah is liable to the penalty of kareis (spiritual excision), as is the woman herself. The penalty for touching her in an affectionate manner (e.g., hugging) was lashes.