Rabanus Maurus
Catena Aurea · Matthäusevangelium 7
Or what man is there of you, whom if his son ask bread, will he give him a stone? Or if he ask a fish, will he give him a serpent? If ye 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?
Or; bread which is the common food signifies charity, without which the other virtues are of no avail. The fish signifies faith, which is born of the water of baptism, is tossed in the midst of the waves of this life and yet lives. Luke adds a third thing, an egg, (Luke 11:12.) which signifies hope; for an egg is the hope of the animal. To charity, He opposes a stone, that is, the hardness of hatred; to faith, a serpent, that is, the venom of treachery; to hope, a scorpion, that is, despair, which stings backward, as the scorpion.