Leviticus 20:18
And if a man shall lie with a woman having her sickness, and shall uncover her nakedness; he hath discovered her fountain, and she hath uncovered the fountain of her blood: and both of them shall be cut off from among their people. And if a man shall lie with a woman having her sickness, and shall uncover her nakedness; he hath discovered her fountain, and she hath uncovered the fountain of her blood: and both of them shall be cut off from among their people.
Intercourse with a woman during her menstrual impurity is prohibited and is ranked among the forbidden sexual relations. That prohibition stands within the laws against incestuous unions and marriages contracted in violation of the forbidden degrees of kinship. The laws of this chapter display what such condemned sexual and spiritual practices did to the nations dwelling in Canaan, upon whom they brought grave consequences.
These prohibitions continue in force because they are grounded in moral considerations. They illuminate the exclusion pronounced in Deuteronomy 23:2, indicating that its term denotes the offspring of such forbidden unions rather than every child born outside marriage. The record of the evil effects of those practices stands as a warning against the dangers of spiritualism.