Ellicott's Commentary for English Readers - Romans 12:20
(20) Thou shalt heap coals of fire.—Comp. Psalms 18:12-14, where the phrase “coals of fire” is used of the divine vengeance. So here, but in a strictly metaphorical sense, it means, “Thou shalt take the best and most summary vengeance upon him.” There may be the underlying idea of awakening in the adversary the pangs of shame and remorse. read more
Ellicott's Commentary for English Readers - Romans 12:9-21
(9-21) Now follow to the end of the chapter a number of general exhortations, not addressed to particular persons or classes, but to the Church at large. read more