Then the Pharisees and Sadducees came, and testing Him asked that He would show them a sign from heaven. 2 He answered and said to them, “When it is evening you say, ‘It will be fair weather, for the sky is red’; 3 and in the morning, ‘It will be foul weather today, for the sky is red and threatening.’ Hypocrites! You know how to discern the face of the sky, but you cannot discern the signs of the times. 4 A wicked and adulterous generation seeks after a sign, and no sign shall be given to it except the sign of the prophet Jonah.” And He left them and departed. — Matthew 16:1-4.
Jesus refers them to a literal sign from heaven, the sky itself. They knew that a red sky in the evening meant fair weather the next day; but a red sky in the morning was an indication of stormy weather ahead. Jesus rebukes them because they could read the signs of the sky but couldn’t read the signs of the times.
Jesus’ analogy shows that the problem was not lack of evidence, but an unwillingness on their part to accept its significance. Jesus had performed many signs already.
Jesus goes on to say that no sign except that of the prophet Jonah would be given them. They would have had no clue as to what He was talking about! Jonah was as good as dead and then restored to life again, and the Son of Man’s rising from the dead is the greatest sign of all that the kingdom has come.
Jesus saw Jonah as a symbol or type of the Christ or Messiah He claimed to be. Jesus had previously explained it. “For as Jonah was three days and three nights in the belly of the great fish, so likewise the Son of Man will be three days and three nights in the heart of the earth.” (Matthew 12:38-40). Jesus is referring to his coming death and resurrection.