3 Let us then acknowledge, beloved brethren, the wholesome gift of the divine mercy; and let us, who cannot be without some wound of conscience, heal our wounds by the spiritual remedies for the cleansing and purging of our sins. Nor let any one so flatter himself with the notion of a pure and immaculate heart, as, in dependence on his own innocence, to think that the medicine needs not to be applied to his wounds; since it is written, “Who shall boast that he has a clean heart, or who shall boast that he is pure from sins?” And again, in his epistle, John lays it down, and says, “If we say that we have no sin, we deceive ourselves, and the truth is not in us.” But if no one can be without sin, and whoever should say that he is without fault is either proud or foolish, how needful, how kind is the divine mercy, which, knowing that there are still found some wounds in those that have been healed, even after their healing, has given wholesome remedies for the curing and healing of their wounds anew!
Source: The Treatises of Cyprian (New Advent)