Leviticus 15:28-31

28When a woman is cleansed of her discharge, she must count off seven days, and after that she will be ceremonially clean. 29On the eighth day she is to take two turtledoves or two young pigeons and bring them to the priest at the entrance to the Tent of Meeting. 30The priest is to sacrifice one as a sin offering and the other as a burnt offering. In this way the priest will make atonement for her before the LORD for her unclean discharge.

31You must keep the children of Israel separate from their uncleanness, so that they do not die by defiling My tabernacle, which is among them.