This scripture applies to the people of Isaiah’s day. It applies to many of our day. It specifically applies to the people of Jesus’ day,
’But though he had done so many miracles before them, yet they believed not on him:
Therefore they could not believe, because that Esaias said again,
He hath blinded their eyes, and hardened their heart; that they should not see with their eyes, nor understand with their heart, and be converted, and I should heal them.
These things said Esaias, when he saw his glory, and spake of him.’ (Jn 12:37,39-41)
’And Jesus said, For judgment I am come into this world, that they which see not might see; and that they which see might be made blind.
And some of the Pharisees which were with him heard these words, and said unto him, Are we blind also?
Jesus said unto them, If ye were blind, ye should have no sin: but now ye say, We see; therefore your sin remaineth.’ (Jn 9:39-41)
The Savior chastises the Pharisees because they considered themselves wise, perceptive, and spiritually enlightened. They were actually the hard-hearted, spiritually blind, and spiritually deaf that Isaiah had prophesied about. The Savior explained that had they recognized their inadequacies (by admitting that they were spiritually blind), they would have had no sin. But they had no such humility. Their pride and self-righteousness was unabated, therefore their ’sin remaineth.’
"The words the prophet Isaiah was commissioned to deliver were in part to bring the people to a full accountability for their choices, so that they would be left without excuse…The people claimed to hear and see, but they did not understand the spirit of the message.
“The command to ’make the heart of this people fat,…their ears heavy, and shut their eyes’ is used to describe the process of making the people accountable.” (1981 Old Testament Institute Manual, p. 144)