What significance does the sign of Jonah hold?

The sign of Jonah, mentioned in Luke 11:30, signifies the death and resurrection of Jesus Christ. Just as Jonah spent three days in the belly of the great fish, Jesus would spend three days in the tomb before rising again. This event is pivotal as it assures believers of the validity of Jesus' claims and His mission to save humanity from sin. The Ninevites' repentance at Jonah's preaching foreshadows the call to repentance that Jesus offers, emphasizing the necessity of recognizing His authority and the urgency to respond to the gospel.