What was the consequence of a man having sexual intercourse during his wife's menstruation?

Lev 15 spoke on ritualistic unclean law:

19 When a woman has a discharge, and the discharge in her body is blood, she shall be in her menstrual impurity for seven days, and whoever touches her shall be unclean until the evening.

Click to expand...

24 And if any man lies with her and her menstrual impurity comes upon him, he shall be unclean seven days, and every bed on which he lies shall be unclean.

Click to expand...

The husband was unclean for 7 days.

Lev 18 was on more serious (unclean) law:

6 None of you shall approach any one of his close relatives to uncover nakedness. I am the LORD.

Click to expand...

19 You shall not approach a woman to uncover her nakedness while she is in her menstrual uncleanness. 20 And you shall not lie sexually with your neighbor’s wife and so make yourself unclean with her.

Click to expand...

Moses continued this more serious tone in 20:

17 If a man takes his sister, a daughter of his father or a daughter of his mother, and sees her nakedness, and she sees his nakedness, it is a disgrace, and they shall be cut off in the sight of the children of their people. He has uncovered his sister’s nakedness, and he shall bear his iniquity. 18If a man lies with a woman during her menstrual period and uncovers her nakedness, he has made naked her fountain, and she has uncovered the fountain of her blood. Both of them shall be cut off from among their people.

Click to expand...

Both the husband and wife were to be cut off from among their people.

When a man had sexual intercourse with his wife during her menstruation, what was the consequence?

According to Lev 15:25, the husband would be unclean for 7 days. According to Lev 20:18, the husband and the wife were to be cut off from among their people.

Why this difference?

Perhaps in the former case, the husband did not know that his wife was menstruating.

Gill explained:

[The latter] 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.

Click to expand...