The Greek noun anthrax means a coal or live ember. Occurring only once in the NT (Romans 12:20), it is used in Paul's quotation of Proverbs 25:22: 'heaping burning coals on the head' of an enemy by showing them kindness.
Paul's use of anthrax in Romans 12:20 is one of the most provocative statements about enemy love in Scripture. 'If your enemy is hungry, feed him... in doing this you will heap burning coals on his head.' The 'burning coals' metaphor, drawn from Proverbs, likely describes the shame and burning conscience that genuine kindness produces in an enemy — a shame that can lead to repentance. Rather than repaying evil with evil, believers are to overcome evil with good (v.21). This counter-intuitive wisdom turns human instinct upside down: kindness is the most powerful weapon against hostility.