What does Proverbs 5:12 mean?

This is a statement of regret, spoken by someone who failed to follow Solomon's warning against adultery (Proverbs 5:1–11). Sin tells us that when something feels good, we should do it—rarely do people describe discipline and common sense as "fun." In that sense, falling prey to adultery—or any other sin—is a matter of preferring pleasure over discipline and good teaching. Those who "hate" godly teaching will, one way or another, come to regret it.

At some point, the adulterer will feel remorse (Proverbs 5:4), but regret comes too late. If he had accepted instruction about the evil of adultery and its consequences, he would not be smitten with remorse. Guilt and regret over past actions are hard to bear. That pain is amplified when sin brings permanent consequences. Those might be to our reputation, finances, or relationships. They can also apply to our physical health (Proverbs 5:11).

After betraying Jesus for thirty pieces of silver, Judas Iscariot was filled with remorse, but it was too late. He returned the thirty pieces of silver to the chief priests and elders (Matthew 27:3), and said, "I have sinned by betraying innocent blood" (Matthew 27:4). After throwing down the silver pieces in the temple, he committed suicide (Matthew 27:5). Judas realized that what he'd done could not be undone. Tragically, that led him to despair instead of to godly repentance (2 Corinthians 7:10).