Matthew 12:38-41 NIV
Then some of the Pharisees and teachers of the law said to him, “Teacher, we want to see a sign from you.”
He answered, “A wicked and adulterous generation asks for a sign! But none will be given it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth. 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.
NIV: New International Version