The scribes and Pharisees want to see a sign from Jesus. What exactly were they looking for? Water to wine? Check. Healing thousands of people? Check. Casting out demons that no one else could? Check. None of his many signs up to that point were enough for them; what could he do that would satisfy them? I do not know what they had in mind, whether one of the plagues of Egypt or dividing the Red Sea. Perhaps they did not have anything particular in mind, only that they wanted Jesus to do something to convince them, something greater than what he had already done.
Jesus responds that he will give them a sign: the sign of Jonah. None of the miracles of Jesus were enough for the Pharisees, so Jesus points to his greatest work: the Cross. Perhaps a great magician could have worked some of the miracles that Jesus worked, or at least convince a crowd that he had done so, but no one could accomplish the Cross except Jesus. On the Cross Jesus was tortured, but he forgave his tormentors. He was killed, but he rose from the dead. That was not the work of an illusionist. No human person could fake the Cross.
So the Pharisees will have their perfect sign, and, for the most part, they will still not believe. This is because faith does not come from signs but is an interior gift of the Holy Spirit. Real faith, the kind that does not rely on anything but is itself the bedrock of life, can only be a gift from God. If faith were something we created by our own judgment of the signs, then faith could never be stronger than our own judgment.
When Jonah walked through Nineveh and the whole city repented, it was not because of the eloquence of the preacher. God put repentance in their hearts and they needed nothing more than the small encouragement of Jonah. If God gives you faith, the smallest sign, seen with faith, will be more convincing than any proof ever done. If God has not given you faith, the greatest sign, feeding thousands with a little bread, making the sun dance across the sky, dying on a cross without complaining, will still leave room for doubt. So do not ask for signs from God; ask for faith, for perfect, invisible faith.
