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,.... Her monthly courses, which make her weak and languid, which is forbidden, Leviticus 18:19; this is not to be understood of a man's lying with his wife ignorantly, when in such a condition, for this being the case, he was only unclean seven days, Leviticus 15:24; whereas this made him and her liable to cutting off, as in an after clause; but of his lying with her, knowing this to be the case with her, and of which she could not be ignorant, and therefore both liable to the same punishment; or else of any other man lying with her, or of any man lying with any woman, married or unmarried, being in such circumstances:
and shall uncover her nakedness; that is, have carnal knowledge of her:
he hath discovered her fountain; from whence her issue of blood flows: and she hath uncovered the fountain of her blood; freely and willingly, as Aben Ezra observes; for if she had been forced, he alone would have been cut off; but both these phrases put together show agreement in this matter, that they both had knowledge of her case, and both consented to commit the sin:
and both of them shall be cut off from among their people; by death, either by the hand of the civil magistrate, the case being known and proved, or else by the hand of God being known by mortality or the pestilence, as the Targum of Jonathan, or they should die childless;
See Gill on "Leviticus 20:17".