2 For this cause have we who are evil a good Father, that we may not always continue evil. No evil man can make another man good. If no evil man can make another good, how can an evil man make himself good? He only can make of an evil man a good man, who is good eternally. “Heal me, and I shall be healed; save me, and I shall be saved.” Why then do those vain ones say to me in words vain as themselves, “You can save yourself if you will”? “Heal me, O Lord, and I shall be healed.”
We were created good by The Good; for “God made man upright,” but by our own free will, we became evil. We had power from being good to become evil, and we shall have power from being evil to become good. But it is He who is ever Good, who makes the good out of the evil; for man by his own will had no power to heal himself. Thou dost not look out for a physician to wound yourself; but when you have wounded yourself, you look out for one to cure you. Good things then after the time present, temporal good things, such as are concerned with the body and flesh, we do know how to give to our children, even though we are evil.
For even these are good things, who would doubt it? A fish, an egg, bread, fruit, wheat, the light we see, the air we breathe, all these are good; the very riches by which men are lifted up, and which make them loth to acknowledge other men to be their equals; by which, I say, men are lifted up rather in love of their dazzling clothing, than with any thought of their common nature, even these riches, I repeat, are good; but all these goods which I have now mentioned may be possessed by good and bad alike; and though they be good themselves, yet cannot they make their owners good.
Source: Sermons on Selected Lessons of the New Testament (New Advent)