How virtuous and useful was that which Elisha did. This is compared with that oft-recounted act of the Greeks. John gave up his life for virtue's sake, and Susanna for the same reason exposed herself to the danger of death.
86. What did Elisha follow but virtue, when he brought the army of Syria who had come to take him as captive into Samaria, after having covered their eyes with blindness? Then he said: “O Lord, open their eyes that they may see.” And they saw. But when the king of Israel wished to slay those that had entered and asked the prophet to give him leave to do so, he answered that they whose captivity was not brought about by strength of hand or weapons of war must not be slain, but that rather he should help them by supplying food. Then they were refreshed with plenty of food. And after that those Syrian robbers thought they must never again return to the land of Israel.
87. How much nobler was this than that which the Greeks once did! For when two nations strove one with the other to gain glory and supreme power, and one of them had the opportunity to burn the ships of the other secretly, they thought it a shameful thing to do so, and preferred to gain a less advantage honourably than a greater one in shameful wise. They, indeed, could not act thus without disgrace to themselves, and entrap by this plot those who had banded together for the sake of ending the Persian war. Though they could deny it in word, yet they could never but blush at the thought of it. Elisha, however, wished to save, not destroy, those who were deceived indeed, though not by some foul act, and had been struck blind by the power of the Lord. For it was seemly to spare an enemy, and to grant his life to an adversary when indeed he could have taken it, had he not spared it.
88. It is plain, then, that whatever is seemly is always useful. For holy Judith by seemly disregard for her own safety put an end to the dangers of the siege, and by her own virtue won what was useful to all in common. And Elisha gained more renown by pardoning than he would have done by slaying, and preserved those enemies whom he had taken for greater usefulness.
89. And what else did John have in mind but what is virtuous, so that he could not endure a wicked union even in the king's case, saying: “It is not lawful for you to have her to wife.” He could have been silent, had he not thought it unseemly for himself not to speak the truth for fear of death, or to make the prophetic office yield to the king, or to indulge in flattery. He knew well that he would die as he was against the king, but he preferred virtue to safety. Yet what is more expedient than the suffering which brought glory to the saint.
90. Holy Susanna, too, when threatened with the fear of false witness, seeing herself hard pressed on one side by danger, on the other by disgrace, preferred to avoid disgrace by a virtuous death rather than to endure and live a shameful life in the desire to save herself. So while she fixed her mind on virtue, she also preserved her life. But if she had preferred what seemed to her to be useful to preserve life, she would never have gained such great renown, nay, perhaps— and that would have been not only useless but even dangerous— she might even not have escaped the penalty for her crime. We note, therefore, that whatsoever is shameful cannot be useful, nor, again, can that which is virtuous be useless. For usefulness is ever the double of virtue, and virtue of usefulness.
Source: On the Duties of the Clergy (New Advent)