Matthew 7:10

Or if he ask a fish, will he give him a serpent?] Which is somewhat like a fish, especially an eel. Fish and bread are mentioned, because these were common food; see Mr 6:41

John 21:13 and particularly in Galilee, a fish country, where Christ now was, and from whence he had called his disciples, who were fishermen. In Lu 11:12 it is added, "or if he shall ask an egg, will he offer him a scorpion?" which is used, as the rest, to show the absurdity and inhumanity of such conduct; and that indeed nothing of this kind is to be found among men, unless it be among monsters in nature.