2 I do not doubt that you wish to hear, Beloved, who they are of whom I have spoken in my address, that they should not look for the good without, and should bear with the evil within. If all within are evil, whom do I address? If all within are good, whom did I advise them to bear with being evil? Let me first then with the Lord's assistance get out of this difficulty as best I can. If you consider good perfectly and strictly speaking, none is good but God Alone. You have the Lord saying most plainly, “Why do you call Me good?
There is none Good but One, that is, God.” How then can that marriage feast have good and bad guests, if “none is good but God Alone”? In the first place ye ought to know, that after a certain sort we are all evil. Yes, doubtless after a certain sort are we all evil; but after no sort are we all good. For can we compare ourselves with the Apostles, to whom the Lord Himself said, “If you then being evil know how to give good gifts unto your children?” If we consider the Scriptures, there was but one evil one among the twelve Apostles, with reference to whom the Lord said in a certain place, “And you are clean, but not all.” But yet in addressing them all together, He said, “If you being evil.”
Peter heard this, John heard this, Andrew heard this, all the rest of the eleven Apostles heard it. What did they hear? “If you being evil know how to give good gifts unto your children; how much more shall your Father which is in heaven give good things to them that ask Him?” When they heard that they were evil, they were in despair; but when they heard that God in heaven was their Father, they revived. “You being evil;” what then is due to the evil, but punishment? “How much more shall your Father which is in heaven?” What is due to children but reward. In the name of “evil” is the dread of punishment; in the name of “children” is the hope of heirs.
Source: Sermons on Selected Lessons of the New Testament (New Advent)