Adultery is always stupid. This is never more clearly seen than in the reality of the reaction of the husband who has learned that his wife has committed adultery with another man. His reaction toward that man is predictable. He reacts with jealousy - in fact what is written here is that he reacts with enraged jealousy.
Jealousy, which is referred to in this proverb, is the Hebrew word "qinah." This word means zeal or jealousy. It describes an intense passion and fervor. It describes an emotion that is greater than wrath or anger. Scripture calls this jealousy a rottenness in a man's bones (Prov. 14:30). It is used to speak of a spirit of jealousy that comes upon a man in Numbers 25:11. But the frightening description of this word is that it is used of God's zeal which He has toward his own people - and which He has for accomplishing His own will and purpose. The word is used six different times to speak of the way God's wrath is expressed in judgment. This is a strong word - and is made even stronger by the fact that it is used in connection with the word, "enrages." This word is the Hebrew word "hemah" and it means wrath or heat. It signifies great fury, anger, indignation, poison , or rage. When put together these two words create quite a terrifying description of the emotions that come over a man who learns of an adulterer seeking to destroy his relationship with his wife.
This enraged jealousy moves this man to seek the maximum penalty for adultery. I've watched this in court battles and divorces. The injured party, when given over to this enraged jealousy, wants to make the other person pay everything possible. There is a desire for them to truly pay the highest price possible for their indiscretion. They want a "day of vengeance." That is why adultery is always stupid. It always injures someone - and makes for emotions that rival any in life. The wise man sees this and realizes that no promise of sexual pleasure will ever match the release of rage, anger, and wrath that will come when their deeds become known.