What does Luke 11:29 mean?
Luke is dealing with two specific ways in which the Pharisees and lawyers reject Jesus. The first is by saying that His power to perform miracles comes from Satan; Jesus has successfully proven this is impossible (Luke 11:14–23).Now, Luke addresses the second, which he alluded to earlier: a demand to see more miracles (Luke 11:16). The first group included scribes—experts in the Mosaic law—who had come from Jerusalem (Mark 3:22). It also included Pharisees (Matthew 12:24). Luke simply says that "some of them" in the crowd had these reactions (Luke 11:15–16). Matthew says that "some of the scribes and Pharisees" make a request to see a sign (Matthew 12:38), and Jesus answers with this.
Dr. Darrell Bock explains that in this section, the "sign" is that in the past God's prophets spoke and unlikely parties responded in repentance and God-worship. Jonah declared coming judgment to the Ninevites, who were Assyrians and counted among the cruelest cultures in history. They immediately repented and God stayed His hand for about 180 years (Jonah 3). Jesus continues that Solomon spoke with God's wisdom and the queen of the South responded (1 Kings 10:1–13). The Jewish religious leaders have a choice: respond to their Messiah with repentance or face the judgment of once-pagan Gentiles who rightfully worshiped the God they claim to serve (Luke 11:30–32).
Why is it sinful for the lawyers and Pharisees to ask for a sign? Because Jesus has fully justified His claim to His identity: by performing miracles that specifically fulfill the prophecies in the Jewish Scriptures. He has given sight to the blind (Isaiah 35:5a; Luke 7:21), hearing to the deaf (Isaiah 35:5b; Luke 7:22), and words to the mute (Isaiah 35:6; Luke 11:14), all of which are distinct Messianic prophecies indicated by Isaiah. The lawyers, who are supposed to be the foremost experts in the Hebrew Scriptures, should know this. They should be celebrating the arrival of the Messiah and telling the people that He has come. Instead, they cast doubt on everything He does.