Luke 11:27
This sign is covered in detail in the Gospel of Matthew (below). Jesus responded to the demand for a "sign from heaven" (Luke 11:16). Such a request could only have been motivated by unbelief, especially in view of the many demonstrations of Messianic power already performed by Jesus (Luke 7:20-23). For Luke, Jesus' very presence was a "sign" of God's redemptive activity (Luke 2:34; 11:30).
Just as Jonah's three-day experience in the belly of the great fish had been a sign to the people of Nineveh, so Jesus' resurrection after three days in the tomb would be a sign to the Jews of his day (Luke 11:30).
Jesus refers to "The Queen of the South," (Luke 11:31), that is, the queen of Sheba (modern Yemen), who made a long and difficult journey to visit Solomon (1 Kings 10). Though a heathen, she was a favorable contrast to the people who refused to take notice of Jesus, the "one greater than Solomon," when he was with them. The Ninevites had repented when Jonah preached (Jonah 3:6-10). As with the queen of Sheba, the argument is from the lesser to the greater. People had responded to Solomon and to Jonah (Luke 11:32); how much more should they have responded to the Son of God in their midst!
The woman expressed the common mindset of the day that a woman may be great if she bears a great son. By heaping blessedness on the mother, she was heaping blessedness on the child (Jesus).