Mt 7:7-12
[Jesus said to his disciples,] 7“Ask and it will be given to you; seek and you will find; knock and the door will be opened to you. 8For everyone who asks, receives; and the one who seeks, finds; and to the one who knocks, the door will be opened. 9Which one of you would hand his son a stone when he asks for a loaf of bread, 10or a snake when he asks for a fish? 11If you then, who are wicked, know how to give good gifts to your children, how much more will your heavenly Father give good things to those who ask him.
12“Do to others whatever you would have them do to you. This is the law and the prophets.”
STONE FOR A LOAF, SNAKE FOR A FISH: In contrasting the disposition of the earthly father to that of God, Jesus uses an indelible image: a round piece of bread which resembles a stone and a fish (probably some eel-shaped species) which looks like a snake. The statement is based on the widespread belief that man is innately good, and that even malicious fathers are capable of giving good things to their children. But the statement is provocative since at the same time it insinuates that there can also be earthly fathers who give their sons stones instead of bread.
The case is the same with mothers. Isaiah pictures a mother tender with her child, but is also aware that there are earthly mothers who neglect their children: “Can a mother forget her infant, be without tenderness for the child of her womb? Even should she forget, I will never forget you” (Is 49:15).
Jesus teaches that in the love of the earthly father for his children, there lives something of the Father from whom all fatherhood on earth is named (Eph 3:14). God, who alone is truly good (Mt 19:17), infinitely surpasses all earthly fatherhood or motherhood. He allows his love to be reflected in the love of earthly parents, a love that should never be dimmed by the possible frailty or malice of earthly parents.