Taken from THE CATECHISM EXPLAINED
Written by Fr. Francis Spirago; Edited by Fr. Richard Clarke, SJ
with Nihil Obstat and Imprimatur, New York, 1927
SECTION A: THE COMMANDMENTS
VIII. THE COMMANDMENT TO LOVE OUR ENEMY
We call him our enemy who hates us and seeks to do us harm.
Saul, for instance, was an enemy of the Christians. Those alone can be said to have the love of their neighbor who love their enemies too. [Emphasis in bold added.] A big fire is not extinguished but increased by the wind; so the love of one's neighbor, if it be real, is not destroyed, but deepened, by affronts and offenses on the part of others. If we only love those who love us, we cannot look for any great reward (Matt. v. 46). We love our friends for our own sake, but we love our enemies for God's sake. [Ibid.]
1. We ought to love our enemies because Christ commands it; He says: "Love your enemies, do good to them that hate you; pray for them that persecute and calumniate you" (Matt. v. 44).
Christ has given us the most striking example of the love of our enemies, for on the Cross He prayed for His enemies, and in the Garden of Olives He healed the servant whose ear Peter had cut off. Our heavenly Father Himself sets us an example, for He makes His sun to rise upon the good and bad, and raineth upon the just and the unjust. He who loves his enemy therefore is like to God; he is a true child of his Father in Heaven (Matt. v. 45).
Another reason why we ought to love our enemy is because he also is made after God's image, and is an instrument in His hand.
Our enemy is made after God's likeness. The king's effigy stamped upon the coin, is equally deserving of respect whether the coin be of copper or gold; so we are bound to love and honor the image of God, whether the man who bears it be vicious or virtuous. It is not the sin we love, but the sinner. Man is God's work, sin is man's work; "therefore," says St. Augustine, "love what God has made, not what man has done." We ought also to love our enemy because God uses him as His instrument. Evil men, unwittingly to themselves, are instruments in God's hands. As the physician employs the leech to draw the bad blood from the veins of the sick man, and effect his cure, so God employs our enemies to remove our imperfections (St. Gregory the Great). The evil shapes the good, as file and hammer shape iron: they are to them as the plough to the fallow ground (St. John Chrysostom). They are, moreover, of service to us, by acquainting us with our faults and giving us an opportunity of practicing virtue. Enemies are like bees; they sting, but they produce honey. [Ibid.] When calumny assails you, console yourself with the thought that it is not the worst fruits that the wasps devour. Finally remember that no enemy can really injure one who loves God; for God makes all hostile designs work good to His Own people (Rom. viii. 28). This is exemplified in Joseph's life. The truth will teach you to bear up against persecution.
2. The love of our enemy is shown in this: That we do not revenge ourselves on him, that we return good for evil, that we pray for him and forgive him willingly.
We ought not to revenge ourselves on our enemy. David gives us a beautiful example, for he twice had the opportunity of putting his persecutor King Saul, to death, and on neither occasion did he do him any harm. Our Lord, when He was reviled, did not revile again (1 Pet. ii. 23). Once when Christ was not received in a Samaritan village because He was a Jew, the Apostles were so desirous of revenge that they wanted to call down fire from Heaven. But Our Lord rebuked them, saying: "You know not of what spirit you are" (Luke ix. 55). Vengeance belongs to God, not to us (Rom. xii. 19). We ought to suffer wrong rather than take revenge; we are told, to him that striketh thee on the one cheek offer the other (Luke vi. 29). Be not overcome by evil, but overcome evil by good (Rom. xii. 21). Avenge yourself, as the Saints did, by returning benefits for the evil done you; such vengeance is Divine. St. Stephen prayed for his murderers; he was more grieved for the harm they did to themselves than for the injury they did to him. When the Apostle James, Bishop of Jerusalem, was thrown from the pinnacle of the Temple, he raised himself on his fractured knees to pray for his murderers. We should also be ready to forgive our enemies. King David forgave Semei, when he threw stones at him and cursed him (2 Kings xvi. 10). To do good to one's enemy is a proof of great magnanimity.
3. He who does not revenge himself on his enemy, or who even confers benefits upon him, puts his foe to shame and pacifies him, and will be rewarded by God; whereas he who hates his enemy and revenges himself on him commits a sin.
David by sparing Saul on two several occasions mollified and touched him to such a degree that he shed tears (1 Kings xxiv. 17). Blessed Clement Hofbauer being abused by a woman in the streets of Vienna, went up to her, picked up a handkerchief she had dropped, and spoke kindly to her. She was covered with confusion, and hastily withdrew. Just as the bore-worm, soft as it is, works its way through the hardest wood, so a conciliatory spirit overcomes the bitterest enemy and coarsest calumniator. By conferring benefits on your enemy, you will heap coals of fire upon his head (Rom. xii. 20), that is to say, he can no more resist your kindness than he could burning coals. Thus we are taught to be gentle and peaceable. He who does not revenge himself will be rewarded by God. David bore Semei's curses patiently, saying, "Perhaps the Lord will look upon my affliction, and may render me good for the cursing of this day" (2 Kings xvi. 12). Shortly after he won a signal victory. It is difficult for you to pray for your enemy; but the greater your self-conquest, the greater will be your recompense (St. Augustine). To revenge one's self is a sin; he who does this is like the bee, which revenges itself by stinging, but in doing so, dies. Besides, it is a foolish thing to revenge one's self; it is like the dog who bites the stick with which he is beaten, for we forget that our enemy is but an instrument in God's hand.
4. He who forgives his enemy will obtain forgiveness of his sins from God; but he who will not forgive his enemy God will not forgive.
To forgive one's enemy is a work of mercy and the greatest of all almsgiving (St. Augustine). If we forgive others, we can ask pardon for ourselves, as is expressed in the fifth petition of the Lord's Prayer. God shows mercy to him who willingly forgives his brother. He who does not forgive his brother brings down on himself no blessing when he repeats the Our Father. Christ says: "If you will not forgive men, neither will your heavenly Father forgive you your offenses" (Matt. vi. 15). Remember the parable of the unmerciful servant (Matt. xviii. 23). We are not merely to forgive seven times, but seventy times seven times (v. 22).