Mark 4:12
This is so that even though they see, they will see and yet not perceive. And even though they hear, they will hear and yet not understand. For if they did, they would turn [back to God] again and receive forgiveness."
Luke 8:10
And He said to them, "You [disciples] are being given an understanding of the secrets of the kingdom of God, but the rest of the people [are being told] in parables, so that [even though they appear to be] seeing, they will not [actually] see; and [even though they seem to] hear, they will not understand.
Matthew 13:14-15
So, the prophecy of Isaiah is being fulfilled by them, which says, [Isa. 6:9f] 'You will hear all right, but you will not understand [what you hear]. You will see all right but you will not perceive [what you see].
Romans 11:8
as it has been written [Isa. 19:10], "God gave them a spirit of numbness [i.e., they developed a spiritual insensitivity to God and His word]. [He gave them] eyes to see with [but they would not look], and ears to hear with [but they did not listen]. And they still have this spirit."
John 12:40
"God has blinded their eyes [of understanding] and closed their minds. If He had not done so, they would [be able to] see with their eyes and understand with their minds and turn [to God] so He could heal them [spiritually]."
Acts 28:26-27
saying, [Isa. 6:9-10], 'Go to these people and say, you will hear all right, but you will not understand [what you hear]. You will see all right, but you will not perceive [what you see].