Leviticus 15:31-33

31“This is how you will guard the people of Israel from ceremonial uncleanness. Otherwise they would die, for their impurity would defile my Tabernacle that stands among them.

32These are the instructions for dealing with anyone who has a bodily discharge—a man who is unclean because of an emission of semen

33or a woman during her menstrual period. It applies to any man or woman who has a bodily discharge, and to a man who has sexual intercourse with a woman who is ceremonially unclean.”