Matthew 13:14

In their case the prophecy of Isaiah is being fulfilled, which says,
You will keep on hearing, but will not understand;
You will keep on seeing, but will not perceive;

Isaiah 6:9-10

He said, “Go, and tell this people:
‘Keep on listening, but do not perceive;
Keep on looking, but do not understand.’

Mark 4:12

so that while seeing, they may see and not perceive, and while hearing, they may hear and not understand, otherwise they might return and be forgiven.”

Luke 8:10

And He said, To you it has been granted to know the mysteries of the kingdom of God, but to the rest it is in parables, so that seeing they may not see, and hearing they may not understand.

Ezekiel 12:2

“Son of man, you live in the midst of the rebellious house, who have eyes to see but do not see, ears to hear but do not hear; for they are a rebellious house.

John 12:39-40

For this reason they could not believe, for Isaiah said again,

Acts 28:25-27

And when they did not agree with one another, they began leaving after Paul had spoken one parting word, “The Holy Spirit rightly spoke through Isaiah the prophet to your fathers,

Romans 11:8-10

just as it is written,
God gave them a spirit of stupor,
Eyes to see not and ears to hear not,
Down to this very day.”

2 Corinthians 3:14

But their minds were hardened; for until this very day at the reading of the old covenant the same veil remains unlifted, because it is removed in Christ.

Treasury of Scripture Knowledge

Summary

And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:

Bible References

The prophecy

Isaiah 6:9
He said, “Go, and tell this people:
‘Keep on listening, but do not perceive;
Keep on looking, but do not understand.’
Ezekiel 12:2
“Son of man, you live in the midst of the rebellious house, who have eyes to see but do not see, ears to hear but do not hear; for they are a rebellious house.
Mark 4:12
so that while seeing, they may see and not perceive, and while hearing, they may hear and not understand, otherwise they might return and be forgiven.”
Luke 8:10
And He said, To you it has been granted to know the mysteries of the kingdom of God, but to the rest it is in parables, so that seeing they may not see, and hearing they may not understand.
John 12:39
For this reason they could not believe, for Isaiah said again,
Acts 28:25
And when they did not agree with one another, they began leaving after Paul had spoken one parting word, “The Holy Spirit rightly spoke through Isaiah the prophet to your fathers,
Romans 11:8
just as it is written,
God gave them a spirit of stupor,
Eyes to see not and ears to hear not,
Down to this very day.”
2 Corinthians 3:14
But their minds were hardened; for until this very day at the reading of the old covenant the same veil remains unlifted, because it is removed in Christ.

General references

Leviticus 13:29
“Now if a man or woman has an infection on the head or on the beard,
Deuteronomy 29:4
Yet to this day the Lord has not given you a heart to know, nor eyes to see, nor ears to hear.
Deuteronomy 32:28
For they are a nation lacking in counsel,
And there is no understanding in them.
Proverbs 20:12
The hearing ear and the seeing eye,
The Lord has made both of them.
Ezekiel 17:2
“Son of man, propound a riddle and speak a parable to the house of Israel,
Matthew 24:39
and they did not understand until the flood came and took them all away; so will the coming of the Son of Man be.