6 See other three things: “Who is there of you, whom if his son ask a loaf, will he give him a stone? Or who is there of you of whom if his son ask a fish, will he give him a serpent? Or if he ask an egg, will he offer him a scorpion? If you then, 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!” Let us then again consider these three things, if haply there be not here those three, “faith, hope, charity; but the greatest of these is charity.”
Set down then these three things, a loaf, a fish, an egg; the greatest of these is a loaf. Therefore in these three things do we well understand charity by “the loaf.” On which account He has opposed a stone to a loaf; because hardness is contrary to charity. By “a fish” we understand faith. A certain holy man has said, and we are glad to say it too; “The 'good fish' is a godly faith.” It lives amidst the waves, and is not broken or dissolved by the waves. Amidst the temptations and tempests of this world, lives godly faith; the world rages, yet it is uninjured.
Observe only that serpent is contrary to faith. For My faith is she betrothed to whom it is said in the Song of Songs, “Come from Lebanon, My spouse, coming and passing over to Me from the beginning of faith.” Therefore betrothed too, because faith is the beginning of betrothal. For something is promised by the bridegroom, and by this plighted faith is he held bound. Now to the fish the Lord opposed the serpent, to faith the devil. Wherefore to this betrothed one does the Apostle say, “I have betrothed you to One Husband, to present you a chaste virgin to Christ.”
And, “I fear lest as the serpent beguiled Eve through his subtlety, so your minds also should be corrupted from the purity which is in Christ;” that is, which is in the faith of Christ. For he says, “That Christ may dwell in your hearts by faith.” Therefore let not the devil corrupt our faith, let him not devour the fish.
Source: Sermons on Selected Lessons of the New Testament (New Advent)