Proverbs 25:22 - Ellicott's Commentary On The Whole Bible

Thou shalt heap coals of fire on his head. — Thou shalt make him burn with shame at the thought of the wrong he has done thee. Thus, to bring a sinner to repentance is well-pleasing to the Lord, who shall reward thee for it. This is better far than to indulge resentment, which must bring sorrow to oneself, punishment from God — whose prerogative of vengeance (Romans 12:19) has been usurped — and only serve to harden the offender in his hostility.