What does Proverbs 6:34 mean?

Adding to the afflictions brought by adultery (Proverbs 6:27–33), Solomon speaks of jealousy and revenge against the adulterer. The wronged spouse can be expected to express furious jealousy. Further, those who choose to take revenge as a result aren't inclined to show mercy. This fits into the Bible's warning that sin comes with many consequences, some of which are entirely natural. God does not need to specially arrange revenge against an adulterer: the normal pattern of the world is likely to make that happen, anyway.

History and news cycles overflow with reports of what jealous spouses do when they learn of their spouse's infidelity. It's especially common to read of a man who, in a fit of jealous rage, stabs or shoots the offender. If for no other reason than self-preservation, the violent rage of a wronged husband is something a prospective adulterer ought to consider.

Joseph rejected the seductive pleas of Potiphar's wife to have sexual relations with her. Her revenge took advantage of the natural jealousy of her own husband. She falsely accused Joseph to her husband, and in rage he took Joseph and put him in prison, the place where the king's prisoners were confined (Genesis 39:19–20). Potiphar's reaction is only remarkable in that he didn't have Joseph killed outright—he might have suspected his wife was lying. When Shechem raped Jacob's daughter Dinah, her brothers were enraged. Two of them, Simeon and Levi, took revenge by killing all the males of Shechem's city. We read: "The sons of Jacob came upon the slain and plundered the city, because they [the men of the city] had defiled their sister" (Genesis 34:27). It was anger over David's indifferent reaction to his sister's rape that kindled Absalom's taste for rebellion (2 Samuel 13:20–22, 32; 15:13–14).