36 If a man make prayer with his whole heart, if he groan with the true lamentations and tears of repentance, if be incline the Lord to pardon of his sin by righteous and continual works, he who expressed His mercy in these words may pity such men: “When you turn and lament, then shall you be saved, and shall know where you have been.” And again: “I have no pleasure in the death of him that dies, says the Lord, hut that he should return and live.” And Joel the prophet declares the mercy of the Lord in the Lord's own admonition, when he says: “Turn to the Lord your God, for He is merciful and gracious, and patient, and of great mercy, and repents Him with respect to the evil that He has inflicted.” He can show mercy; He can turn back His judgment.
He can mercifully pardon the repenting, the labouring, the beseeching sinner. He can regard as effectual whatever, in behalf of such as these, either martyrs have besought or priests have done. Or if any one move Him still more by his own atonement, if he appease His anger, if he appease the wrath of an indignant God by righteous entreaty, He gives arms again whereby the vanquished may be armed; He restores and confirms the strength whereby the refreshed faith may be invigorated.
The soldier will seek his contest anew; he will repeat the fight, he will provoke the enemy, and indeed by his very suffering he is made braver for the battle. He who has thus made atonement to God; he who by repentance for his deed, who by shame for his sin, has conceived more both of virtue and of faith from the very grief of his fall, heard and aided by the Lord, shall make the Church which he had lately saddened glad, and shall now deserve of the Lord not only pardon, but a crown.
Source: The Treatises of Cyprian (New Advent)