undoubtedly because Paul cites it in Romans 12:21.27 Verse 22a, with its image of "heaping coals of fire on his head," has been interpreted in various ways. Among the church fathers, Origen and Chrysostrom interpret the line to mean that doing good to one's enemy makes him liable to greater punishment. Augustine and. Jerome, however, interpret the "coals of fire" to mean "burning pangs of shame" which lead to repentance and reconciliation.28 The first understanding seems to be accepted by Scott who takes the "coals of fire" to be "a form of torture."29 Doing good to the enemy is ultimately a more effective way of taking revenge.
The second interpretation is represented by McKane who comments,
Kindness shown to an enemy, because it is undeserved, awakens feelings of remorse. When the enemy has steeled himself to meet hate with hate and is impervious to threats of revenge, he is vulnerable to a generosity which overlooks and forgives, and capitulates to kindness. . . The pain of contrition purifies and recreates;
27 Paul's citation omits the words "bread" and "water" from v. 21 and "the Lord will reward you," from v. 22. In his omission of "bread" and "water" his reading is identical to that of Vaticanus, as is his reading ywmize in place of trefe. His omission of v. 22b may indicate a rejection of doing good for some reward. On the New Testament meaning of this verse see W. Klasg, "Coals of Fire: Sign of Repentance or Revenge?" NTS 9 (1963), 337-350.
28 The patristic interpretations are mentioned by M. Dahood, "Two Pauline Quotations from the Old Testament," CBQ 17 (1955), 19.
Scott, p. 156.