Verses Lv12-02c describes the ritual impurity of a woman who gave birth to a child Speak to the people of Israel, saying, If a woman conceives, and bears a male child; then she shall be unclean seven days; as in the days of her menstruation, shall she be unclean. As is clear from the underlined words, as in the days of her menstruation, this verse cross-references the laws of ritual impurity of the menstruant which are described beginning in Biblical verse Lv15-19: And if a woman has a discharge, and the discharge of her flesh is blood, she shall be put apart seven days; and whoever touches her shall be unclean until the evening. Rashi basically identifies this cross reference: Rashi: The laws of ritual impurity, of the woman who gave birth to a child, are similar to all laws of ritual impurity mentioned in the cross referenced chapter on menstruant ritual impurity.