Matthew 16:1-4 NIV
The Pharisees and Sadducees came to Jesus and tested him by asking him to show them a sign from heaven.
He replied, “When evening comes, you say, ‘It will be fair weather, for the sky is red,’ and in the morning, ‘Today it will be stormy, for the sky is red and overcast.’ You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times. A wicked and adulterous generation looks for a sign, but none will be given it except the sign of Jonah.” Jesus then left them and went away.
NIV: New International Version