Mark 4:12

that 'seeing they may see, and not perceive; and hearing they may hear, and not understand; lest perhaps they should return and be forgiven.'"

Isaiah 6:9-10

He said, "Go, and tell this people, 'You hear indeed, but do not understand; and you see indeed, but do not perceive.'

Jeremiah 5:21

'Hear now this, foolish people, and without understanding; who have eyes, and do not see; who have ears, and do not hear:

Deuteronomy 29:4

but the LORD has not given you a heart to know, and eyes to see, and ears to hear, to this day.

Jeremiah 31:18-20

I have surely heard Ephraim bemoaning himself thus, 'You have chastised me, and I was chastised, as an untrained calf: turn me, and I shall be turned; for you are the LORD my God.

Matthew 13:14-15

And in them the prophecy of Isaiah is fulfilled, which says, 'By hearing you will hear, and will in no way understand; Seeing you will see, and will in no way perceive:

Luke 8:10

He said, "To you it is given to know the mysteries of the Kingdom of God, but to the rest in parables; that 'seeing they may not see, and hearing they may not understand.'

Isaiah 44:18

They do not know, neither do they consider: for he has shut their eyes, that they can't see; and their hearts, that they can't understand.

Ezekiel 12:2

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

Ezekiel 18:27-32

Again, when the wicked man turns away from his wickedness that he has committed, and does that which is lawful and right, he shall save his soul alive.

John 12:37-41

But though he had done so many signs before them, yet they did not believe in him,

Acts 3:19

"Repent therefore, and turn again, that your sins may be blotted out, so that there may come times of refreshing from the presence of the Lord,

Acts 28:25-27

When they did not agree among themselves, they departed after Paul had spoken one word, "The Holy Spirit spoke rightly through Isaiah, the prophet, to your fathers,

Romans 11:8-10

According as it is written, "God gave them a spirit of stupor, eyes that they should not see, and ears that they should not hear, to this very day."

2 Timothy 2:25

in gentleness correcting those who oppose him: perhaps God may give them repentance leading to a full knowledge of the truth,

Hebrews 6:6

and then fell away, it is impossible to renew them again to repentance; seeing they crucify the Son of God for themselves again, and put him to open shame.

Treasury of Scripture Knowledge

Summary

That seeing they may see, and not perceive; and hearing they may hear, and not understand; lest at any time they should be converted, and their sins should be forgiven them.

General references

Bible References

That seeing

Deuteronomy 29:4
but the LORD has not given you a heart to know, and eyes to see, and ears to hear, to this day.
Isaiah 6:9
He said, "Go, and tell this people, 'You hear indeed, but do not understand; and you see indeed, but do not perceive.'
Isaiah 44:18
They do not know, neither do they consider: for he has shut their eyes, that they can't see; and their hearts, that they can't understand.
Jeremiah 5:21
'Hear now this, foolish people, and without understanding; who have eyes, and do not see; who have ears, and do not hear:
Matthew 13:14
And in them the prophecy of Isaiah is fulfilled, which says, 'By hearing you will hear, and will in no way understand; Seeing you will see, and will in no way perceive:
Luke 8:10
He said, "To you it is given to know the mysteries of the Kingdom of God, but to the rest in parables; that 'seeing they may not see, and hearing they may not understand.'
John 12:37
But though he had done so many signs before them, yet they did not believe in him,
Acts 28:25
When they did not agree among themselves, they departed after Paul had spoken one word, "The Holy Spirit spoke rightly through Isaiah, the prophet, to your fathers,
Romans 11:8
According as it is written, "God gave them a spirit of stupor, eyes that they should not see, and ears that they should not hear, to this very day."

Be converted

Jeremiah 31:18
I have surely heard Ephraim bemoaning himself thus, 'You have chastised me, and I was chastised, as an untrained calf: turn me, and I shall be turned; for you are the LORD my God.
Ezekiel 18:27
Again, when the wicked man turns away from his wickedness that he has committed, and does that which is lawful and right, he shall save his soul alive.
Acts 3:19
"Repent therefore, and turn again, that your sins may be blotted out, so that there may come times of refreshing from the presence of the Lord,
2 Timothy 2:25
in gentleness correcting those who oppose him: perhaps God may give them repentance leading to a full knowledge of the truth,
Hebrews 6:6
and then fell away, it is impossible to renew them again to repentance; seeing they crucify the Son of God for themselves again, and put him to open shame.

General references

Proverbs 28:5
Evil men do not understand justice; but those who seek the LORD understand it fully.