Matthew 13:14
And in them is being fulfilled that prophecy of Isaiah which says--'You will hear with your ears without ever understanding, And, though you have eyes, you will see without ever perceiving,
Mark 4:12
'Though they have eyes, they may see without perceiving; And though they have ears, they may hear without understanding; Lest some day they should turn and be forgiven.'
Luke 8:10
"To you," he said, "the knowledge of the hidden truths of the Kingdom of God has been imparted, but to others in parables only, that 'though they have eyes they may not see, and though they have ears, they may not understand.'
John 12:39-40
The reason why they were unable to believe is given by Isaiah elsewhere, in these words--
Acts 28:25-27
So, as they disagreed among themselves, they began to disperse, Paul adding only--"True, indeed, was the declaration made by the Holy Spirit, through the Prophet Isaiah to your ancestors--
Romans 11:8-10
The rest grew callous; as Scripture says--'God has given them a deadness of mind--eyes that are not to see and ears that are not to hear--and it is so to this very day.'
2 Corinthians 3:14
But their minds were slow to learn. Indeed, to this very day, at the public reading of the Old Covenant, the same veil remains unlifted; only for those who are in union with Christ does it pass away.