9 And I have heard many, after such experience, blame themselves, and say, What advantage is it that I have grieved? I have not recovered my money, and I have injured myself. But if you have grieved on account of sin, you have blotted it out, and hast reaped the greatest pleasure. If you have grieved for your brethren who have fallen, you have both encouraged and comforted yourself, and hast also restored them; and even if you were not to profit them, you have an abundant recompense.
And that you may learn that this grieving for those who have fallen, though we should not at all benefit them, still brings us a large reward, hear what Ezekiel says; or rather, what God Himself speaks through him. For when He had sent certain messengers to overturn the city, and to consume all the dwellings with sword and fire, along with their inhabitants, He thus charges one of them: “Set a mark upon the forehead of the men that groan, and are in anguish.” And after charging the others, and saying, “Begin ye from mine holy ones,” He goes on to add, “But upon whomsoever the sign is, touch them not.” For what reason, tell me?
Because although they avail nothing, they nevertheless lament the things which are done, and deplore them. And again, He accuses others, saying, That in their luxury, and gluttony, and enjoyment of great security, when they beheld the Jews carried away into captivity, they did not grieve, nor partake of their sadness. And hear what He says, reproaching them: “They suffered nothing in the affliction of Joseph:” meaning by Joseph the whole people. And again: “The inhabitants of Ænan went not forth to bewail the house next unto them.” For although they are justly punished, God wills that we should condole with them, and not rejoice or insult.
“For if I that punish,” says He, do not this rejoicingly; nor take pleasure in their punishment; for “I do not at all will the death of the sinner;” it is right that you should imitate your Lord; and should mourn for this very thing, that the sinner has provided matter and occasion for a just punishment. So that if any one entertains a godly sorrow, he will thence reap a great advantage.
Source: Homilies on the Statues (New Advent)