Moreover the Lord tells us in the gospel, “the men of Nineveh shall rise in judgment with this generation and shall condemn it: because they repented at the preaching of Jonas;” and again He says “I am not come to call the righteous but sinners to repentance.” The lost piece of silver is sought for until it is found in the mire. So also the ninety and nine sheep are left in the wilderness, while the shepherd carries home on his shoulders the one sheep which has gone astray. Wherefore also “there is joy in the presence of the angels over one sinner that repents.” What a blessed thought it is that heavenly beings rejoice in our salvation! For it is of us that the words are said: “Repent ye: for the kingdom of heaven is at hand.” Death and life are contrary the one to the other; there is no middle term. Yet penitence can knit death to life. The prodigal son, we are told, wasted all his substance, and in the far country away from his father “would fain have filled his belly with the husks that the swine did eat.” Yet, when he comes back to his father, the fatted calf is killed, a robe and a ring are given to him. That is to say, he receives again Christ's robe which he had before defiled, and hears to his comfort the injunction: “let your garments be always white.” He receives the signet of God and cries to the Lord: “Father, I have sinned against heaven and before you;” and receiving the kiss of reconciliation, he says to Him: “Now is the light of your countenance sealed upon us, O Lord.”
Hear the words of Ezekiel: “as for the wickedness of the wicked, he shall not fall thereby in the day that he turns from his wickedness; neither shall the righteous be able to live for his righteousness in the day that he sins.” The Lord judges every man according as he finds him. It is not the past that He looks upon but the present. Bygone sins there may be, but renewal and conversion remove them. “A just man,” we read “falls seven times and rises up again.” If he falls, how is he just? And if he is just, how does he fall? The answer is that a sinner does not lose the name of just if he always repents of his sins and rises again. If a sinner repents, his sins are forgiven him not only till seven times but till seventy times seven. To whom much is forgiven, the same loves much. The harlot washed with her tears the Saviour's feet and wiped them with her hair; and to her, as a type of the Church gathered from the nations, was the declaration made: “Your sins are forgiven.” The self-righteous Pharisee perished in his pride, while the humble publican was saved by his confession.
God makes asseveration by the mouth of the prophet Jeremiah: “At what instant I shall speak concerning a nation and concerning a kingdom, to pluck up, to pull down and to destroy it: if that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them. And at what instant I shall speak concerning a nation, and concerning a kingdom to build and to plant it; if it do evil in my sight, that it obey not my voice, then I will repent of the good wherewith I said I would benefit them.” And immediately he adds: “Behold, I frame evil against you, and devise a device against you: return ye now every one from his evil way, and make your ways and your doings good. And they said, there is no hope: but we will walk after our own devices, and we will every one do the imagination of his evil heart.” The righteous Simeon says in the gospel: “Behold, this child is set for the fall and rising again of many,” for the fall, that is, of sinners and for the rising again of the penitent. So the apostle writes to the Corinthians: “it is reported commonly that there is fornication among you, and such fornication as is not so much as named among the Gentiles, that one should have his father's wife. And you are puffed up and have not rather mourned that he that has done this deed might be taken away from among you.” And in his second epistle to the same, “lest such a one should be swallowed up with overmuch sorrow,” he calls him back, and begs them to confirm their love towards him, so that he who had been destroyed by incest might be saved by penitence.
“There is no man clean from sin; even though he has lived but for one day.” And the years of man's life are many in number. “The stars are not pure in his sight, and his angels he charged with folly.” If there is sin in heaven, how much more must there be sin on earth? If they are stained with guilt who have no bodily temptations, how much more must we be, enveloped as we are in frail flesh and forced to cry each one of us with the apostle: “O wretched man that I am! Who shall deliver me from the body of this death? For in my flesh there dwells no good thing.” For we do not what we would but what we would not; the soul desires to do one thing, the flesh is compelled to do another. If any persons are called righteous in scripture, and not only righteous but righteous in the sight of God, they are called righteous according to that righteousness mentioned in the passage I have quoted: “A just man falls seven times and rises up again,” and on the principle laid down that the wickedness of the wicked shall not hurt him in the day that he turns to repentance. In fact Zachariah the father of John who is described as a righteous man sinned in disbelieving the message sent to him and was at once punished with dumbness. Even Job, who at the outset of his history is spoken of as perfect and upright and uncomplaining, is afterwards proved to be a sinner both by God's words and by his own confession. If Abraham, Isaac, and Jacob, the prophets also and the apostles were by no means free from sin and if the finest wheat had chaff mixed with it, what can be said of us of whom it is written: “What is the chaff to the wheat, says the Lord?” Yet the chaff is reserved for future burning; as also are the tares which at present are mingled with the growing grain. For one shall come whose fan is in His hand, and shall purge His floor, and shall gather His wheat into the garner, and shall burn the chaff in the fire of hell.
4. Roaming thus through the fairest fields of scripture I have culled its loveliest flowers to weave for your brows a garland of penitence; for my aim is that, flying on the wings of a dove, you may find rest and make your peace with the Father of mercy. Your former wife, who is now your sister and fellow-servant, has told me that, acting on the apostolic precept, you and she lived apart by consent that you might give yourselves to prayer; but that after a time your feet sank beneath you as if resting on water and indeed— to speak plainly— gave way altogether. For her part she heard the Lord saying to her as to Moses: “as for you stand thou here by me;” and with the psalmist she said of Him: “He has set my feet upon a rock.” But your house— she went on— having no sure foundation of faith fell before a whirlwind of the devil. Hers however still stands in the Lord, and does not refuse its shelter to you; you can still be joined in spirit to her to whom you were once joined in body. For, as the apostle says, “he that is joined unto the Lord is one spirit” with him. Moreover, when the fury of the barbarians and the risk of captivity separated you again, you promised with a solemn oath that, if she made her way to the holy places, you would follow her either immediately or later, and that you would try to save your soul now that by your carelessness you had seemed to lose it. Perform, now, the vow which you then made in the presence of God. Human life is uncertain. Therefore, lest you may be snatched away before you have fulfilled your promise, imitate her whose teacher you ought to have been. For shame! The weaker vessel overcomes the world, and yet the stronger is overcome by it!
Source: Letters (New Advent)