Barnes
A revenger ... - In Rom_12:19, vengeance is said to belong to God. Yet he “executes†his vengeance by means of subordinate agents. It belongs to him to take vengeance by direct judgments, by the plague, famine, sickness, or earthquakes; by the appointment of magistrates; or by letting loose the passions of people to prey upon each other. When a magistrate inflicts punishment on the guilty, it is to be regarded as the act of God taking vengeance “by him;†and on this principle only is it right for a judge to condemn a man to death. It is not because one man has by nature any right over the life of another, or because “society†has any right collectively which it has not as individuals; but because “God†gave life, and because he has chosen to take it away when crime is committed by the appointment of magistrates, and not by coming forth himself visibly to execute the laws. Where “human†laws fail, however, he often takes vengeance into his own hands, and by the plague, or some signal judgments, sweeps the guilty into eternity.