Mark 4:12

that seeing they may see, and not perceive; and hearing they may hear, and not understand; lest haply they should turn again, and it should be forgiven them.

Isaiah 6:9-10

And he said, Go, and tell this people, Hear ye indeed, but understand not; and see ye indeed, but perceive not.

Jeremiah 5:21

Hear now this, O foolish people, and without understanding; that have eyes, and see not; that have ears, and hear not:

Deuteronomy 29:4

but Jehovah hath not given you a heart to know, and eyes to see, and ears to hear, unto this day.

Jeremiah 31:18-20

I have surely heard Ephraim bemoaning himself thus , Thou hast chastised me, and I was chastised, as a calf unaccustomed to the yoke : turn thou me, and I shall be turned; for thou art Jehovah my God.

Matthew 13:14-15

And unto them is fulfilled the prophecy of Isaiah, which saith, By hearing ye shall hear, and shall in no wise understand; And seeing ye shall see, and shall in no wise perceive:

Luke 8:10

And he said, Unto 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 know not, neither do they consider: for he hath shut their eyes, that they cannot see; and their hearts, that they cannot understand.

Ezekiel 12:2

Son of man, thou dwellest in the midst of the rebellious house, that have eyes to see, and see not, that have ears to hear, and hear not; for they are a rebellious house.

Ezekiel 18:27-32

Again, when the wicked man turneth away from his wickedness that he hath committed, and doeth 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 believed not on him:

Acts 3:19

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

Acts 28:25-27

And when they agreed not among themselves, they departed after that Paul had spoken one word, Well spake the Holy Spirit through Isaiah the prophet unto 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, unto this very day.

2 Timothy 2:25

in meekness correcting them that oppose themselves; if peradventure God may give them repentance unto the knowledge of the truth,

Hebrews 6:6

and then fell away, it is impossible to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an 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 Jehovah hath not given you a heart to know, and eyes to see, and ears to hear, unto this day.
Isaiah 6:9
And he said, Go, and tell this people, Hear ye indeed, but understand not; and see ye indeed, but perceive not.
Isaiah 44:18
They know not, neither do they consider: for he hath shut their eyes, that they cannot see; and their hearts, that they cannot understand.
Jeremiah 5:21
Hear now this, O foolish people, and without understanding; that have eyes, and see not; that have ears, and hear not:
Matthew 13:14
And unto them is fulfilled the prophecy of Isaiah, which saith, By hearing ye shall hear, and shall in no wise understand; And seeing ye shall see, and shall in no wise perceive:
Luke 8:10
And he said, Unto 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 believed not on him:
Acts 28:25
And when they agreed not among themselves, they departed after that Paul had spoken one word, Well spake the Holy Spirit through Isaiah the prophet unto 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, unto this very day.

Be converted

Jeremiah 31:18
I have surely heard Ephraim bemoaning himself thus , Thou hast chastised me, and I was chastised, as a calf unaccustomed to the yoke : turn thou me, and I shall be turned; for thou art Jehovah my God.
Ezekiel 18:27
Again, when the wicked man turneth away from his wickedness that he hath committed, and doeth that which is lawful and right, he shall save his soul alive.
Acts 3:19
Repent ye therefore, and turn again, that your sins may be blotted out, that so there may come seasons of refreshing from the presence of the Lord;
2 Timothy 2:25
in meekness correcting them that oppose themselves; if peradventure God may give them repentance unto the knowledge of the truth,
Hebrews 6:6
and then fell away, it is impossible to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.

General references

Proverbs 28:5
Evil men understand not justice; But they that seek Jehovah understand all things.

American Standard Version Public Domain