The Pharisees and Sadducees came to Jesus. In order to test him they asked him to show them a sign from heaven.
References for Matthew 16:1
But he replied, "At evening you say, ‘It will be nice weather because the sky is bright red.'
And in the morning you say, ‘There will be bad weather today because the sky is cloudy.' You know how to make sense of the sky's appearance. But you are unable to recognize the signs that point to what the time is.
An evil and unfaithful generation searches for a sign. But it won't receive any sign except Jonah's sign." Then he left them and went away.