Matthew 12:38

Then certain of the scribes and Pharisees answered him, saying, Teacher, we would see a sign from thee.

This arrogant request came from a group who had already accused Jesus of being in league with the devil and who had already seen signs aplenty; but in this case, they were demanding a sign of their own choosing. Luke stated that they sought a "sign from heaven" (Luke 11:16). By that, they no doubt meant some spectacular wonder without moral value but which would appeal sensationally to a man's curiosity. Christ always rejected that type of sign, as, for example, when he refused to jump from the pinnacle of the temple (Matthew 4:6). In fact, there is more than a suggestion that the Pharisees' request for a sign was but a renewal of Satan's temptation of the Lord in the wilderness. Christ always refused to perform wonders for his enemies like Herod or the Pharisees. He did work miracles for the benefit of John's disciples (Luke 7:18-22), and raised Lazarus that the people might believe (John 11:42). For more on "a sign from heaven," see under Matthew 16:1.