Leviticus 12 explicitly compares the mother’s initial postpartum impurity period to the impurity of menstruation. Leviticus 15 gives the fuller rules for menstrual discharge and associated impurity, so the later chapter supplies the ritual category Leviticus 12 uses as its comparison point. The link is internal Torah clarification, not moral condemnation of childbirth.

Genesis 17 commands circumcision on the eighth day; Leviticus 12:3 repeats that same timing inside the childbirth-purity instructions. The later law therefore carries the Abrahamic covenant sign forward rather than creating a new circumcision schedule.