These sayings flow from the previous instruction to seek God. God will open the door, but what will be on the other side? Since the context has become one of petition through prayer, we are now asking of God, and the question becomes one of what response God will have to our petitions. These sayings describe the result.
Old World Context: There are two pairings here, stone/bread and fish/serpent. The connection between the pairings is similarity of shape (Robert Guelich. A Foundation for Understanding the Sermon on the Mount. Word Publishing, Dallas. 1982, p. 358). The common loaf of bread was round and raised, and somewhat similar in shape to a smooth stone. The fish was probably a common eel-like fish that could resemble a serpent. Both bread and fish were the staples of the Galilean diet, and therefore quite appropriate in prayer (remember the “give us this day our daily bread” of the Matthean Lord’s Prayer). The examples are given to be unthinkable. No father would misunderstand what his son wanted when asking for food, and give him instead something that appeared as food but was not.
The phrase “if ye then, being evil,” refers to our position before God. Since the comparison will be to God, we certainly cannot be equated with God, and therefore the conceptual distance is emphasized by noting that we are evil to God’s good. This is not to suggest that we are actually evil, but only that we contrast with God’s goodness. Since we mere mortals understand how to give appropriately when our sons ask of us, God our Father will so much more understand and desire to receive and answer our prayers with what we need.
Textual: There are no changes from the Matthean text.