"If your enemy is hungry, give him bread to eat, and if he is thirsty, give him water to drink" (Proverbs 25:21). Rabbi Hama bar Hanina said: Even though he rose early to kill you, if he comes hungry and thirsty into your house, feed him and give him drink. Why? "For you will be heaping coals upon his head, and the LORD will repay you" (Proverbs 25:22) - do not read "will repay you" [yeshallem lakh], but rather "will make him at peace with you" [yashlimennu lakh].
Feeding the Enemy Who Came to Kill You
Midrash Mishlei 25:5
(משלי כה כא): "אם רעב שונאך האכילהו לחם, ואם צמא השקהו מים" - אמר רבי חמא בר חנינא: אף על פי שהשכים להרגך, ובא רעב וצמא לתוך ביתך, האכילהו והשקהו; למה? (משלי כה כב): "כי גחלים אתה חותה על ראשו, וה' ישלם לך" - אל תקרי ישלם לך, אלא ישלימנו לך.