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.
The Pharisees and the Sadducees were bitter rivals, and for these two groups to work together against Jesus is a bad sign. They came to Him demanding a sign from heaven to confirm His authority to preach, as though they didn’t already know about the miracles and signs He has provided. Can anyone be foolish enough to think that if Jesus performed one more miracle, these groups would change their minds about Him?
Of course not, they’d just demand another sign!
Apparently both groups saw Jesus as a serious threat; so serious in fact, that they were willing to stop fighting each other to team up against Jesus.
Jesus isn’t giving them a sign. Of all of the people of Israel, both the Pharisees and the Sadducees should have known who He was, and my guess is that they did know who He was. There would only be one sign for their wicked generation, the sign of Jonah.
Jesus used this same language in chapter 12, and here is the explanation:
Then some of the Pharisees and teachers of the law said to him, “Teacher, we want to see a sign from you.”
He answered, “A wicked and adulterous generation asks for a sign! But none will be given it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth. The men of Nineveh will stand up at the judgment with this generation and condemn it; for they repented at the preaching of Jonah, and now something greater than Jonah is here.
Jesus has performed many miracles for those who had faith in Him; for those who refuse, there will be only one sign: He will rise from the dead, and that is their only chance to respond. Jesus is not going to play their games.
Of course, He has more to say in the next section…