What caused this anger and grief? It was their hardness of heart.

This is an excerpt from a sermon by Spurgeon.

What was their exact fault?

First, they would not see, though the case was clear. He had set the truth so plainly before them that they were obliged to strain their understandings to avoid being convinced: they had to draw down the blinds of the soul, and put up the shutters of the mind, to be able not to see. There are none so blind as those that will not see, and these were of that blindest order; they were blind people that had eyes and boasted that they could see, and therefore their sin was utterly without excuse. Ah, me! I fear that we have many around us still, who know, but do not act on their knowledge; who do not wish to be convinced and converted, but harden themselves against known duty and plain right.

What was more, what these people were forced to see they would not acknowledge. They sullenly held their tongues when they were bound to speak. Does it not happen to many persons that the gospel forces itself upon their belief? They feel that they could not conjure up an argument against the divine truth which is set before them: the word comes with such demonstration that it smites them with sledge-hammer force; but they do not intend to admit its power, and so they brace themselves up to bear the blow without yielding. They shut their months against the water of life which is held up to them in the golden cup of the gospel. No child could shut his teeth more desperately against medicine than they against the gospel. Any man may take a horse to the water, but ten thousand cannot make him drink, and this is proved in many a hearer of the word. There sat these Scribes and Pharisees: it is a wonder that the stones did not cry out against them, they were so doggedly determined not to admit that which they could not deny. Are there none of that breed among us still?

More than that, while they would not see what was so plain, they were diligently seeking to spy out flaws and faults where there were none, namely, in the Lord Jesus. So there are many who profess that they cannot understand the gospel, but they have understanding enough to cavil at it, and cast slurs upon it. They have a cruelly keen eye for non-existent errors in Scripture: they find this mistake in Deuteronomy, and the other in Genesis. What great wisdom, to be diligent in making discoveries against one's own eternal interests! The gospel of the Lord Jesus is man's only hope of salvation: what a pity to count it the height of cleverness to destroy our only hope!

Spurgeon's Sermon "Jesus Angry with Hard Hearts"

Luke 16:31
"He said to him, 'If they do not listen to Moses and the Prophets, they will not be convinced even if someone rises from the dead.' "