As the crowds increased, Jesus said, “This is a wicked generation. It asks for a sign, but none will be given it except the sign of Jonah. For as Jonah was a sign to the Ninevites, so also will the Son of Man be to this generation. The Queen of the South will rise at the judgment with the people of this generation and condemn them, for she came from the ends of the earth to listen to Solomon’s wisdom; and now something greater than Solomon is here. The men of Nineveh will stand up at the judgment with this generation and condemn it, for they repented at the preaching of Jonah; and now something greater than Jonah is here.
Jesus was showing the connection between the Old Testament and himself; showing that he knew entirely the teachings of the Jewish religion and that He had come to fulfil the prophecies. Jesus is telling how people will now move to God's side even more than they did in Nineveh. And so it was and is still today.