But he answered them, “An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah. For just as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth. The men of Nineveh will rise up at the judgment with this generation and condemn it, for they repented at the preaching of Jonah, and behold, something greater than Jonah is here.
This was the answer to a question. What was the question?
Matthew 12:38 Then some of the scribes and Pharisees answered him, saying, “Teacher, we wish to see a sign from you.”
Some answered a question with a question. This is a sign of lack of understanding. What did Jesus ask of them that they could not answer?
Matthew 12:34 You brood of vipers! How can you speak good, when you are evil? For out of the abundance of the heart the mouth speaks.
It all begins with the condition of the heart and that evil generation did not know their own hearts.
Luke 18:9-14 English Standard Version
The Pharisee and the Tax Collector
9 He also told this parable to some who trusted in themselves that they were righteous, and treated others with contempt: 10 “Two men went up into the temple to pray, one a Pharisee and the other a tax collector. 11 The Pharisee, standing by himself, prayed thus: ‘God, I thank you that I am not like other men, extortioners, unjust, adulterers, or even like this tax collector. 12 I fast twice a week; I give tithes of all that I get.’ 13 But the tax collector, standing far off, would not even lift up his eyes to heaven, but beat his breast, saying, ‘God, be merciful to me, a sinner!’ 14 I tell you, this man went down to his house justified, rather than the other. For everyone who exalts himself will be humbled, but the one who humbles himself will be exalted.”
The one who knows the condition of his heart and confesses he is unworthy and seeks mercy will find it.
While it was too late for the Pharisee, it is not too late for any sinner who confesses and seeks mercy from God through faith in the Lamb who was slain as the sign of Jonah.
How is your heart?