Mark 4:12

that when they see, they shall see, and not discern: and when they hear they shall hear, and not understand: lest at any time they should turn, and their sins should be forgiven them."

Isaiah 6:9-10

And so he said, "Go, and tell this people: 'Ye shall hear indeed, but ye shall not understand; ye shall plainly see, and not perceive.

Jeremiah 5:21

"Hear this, thou foolish and indiscreet people: ye have eyes, but ye see not; ears have ye, but ye hear not.

Deuteronomy 29:4

And yet the LORD hath not given you a heart to perceive, nor eyes to see, nor ears to hear unto this day.

Jeremiah 31:18-20

Moreover, I heard Ephraim, that was led away captive, complain on this manner, 'O LORD, thou hast corrected me, and thy chastening have I received, as an untamed calf. Convert thou me, and I shall be converted, for thou art my LORD God.

Matthew 13:14-15

And in them is fulfilled the prophecy of Isaiah, which prophecy saith, 'With the ears ye shall hear, and shall not understand; and with the eyes ye shall see, and shall not perceive."

Luke 8:10

And he said, "Unto you is it given to know the secrets of the kingdom of God: but to others in similitudes, that when they see, they should not see, and when they hear they should not understand.

Isaiah 44:18

Yet men neither consider nor understand; because their eyes are stopped that they cannot see, and their hearts, that they can not perceive.

Ezekiel 12:2

"Thou son of man, thou dwellest in the midst of a froward household: which have eyes to see, and yet see not; ears have they to hear, and yet hear they not. For they are an obstinate household.

Ezekiel 18:27-32

And when a wicked turneth from his wickedness and doth justly and righteously, he shall save his soul:

John 12:37-41

And though he had done so many miracles before them, yet believed not they on him,

Acts 3:19

Repent ye, therefore, and turn: that your sins may be done away when the time of refreshing cometh, which we shall have of the presence of the Lord,

Acts 28:25-27

When they agreed not among themselves, they departed, after that Paul had spoken one word, "Well spake the holy ghost by Isaiah the prophet unto our fathers,

Romans 11:8-10

according as it is written, "God hath given them the spirit of unquietness: eyes that they should not see, and ears that they should not hear, even unto this day."

2 Timothy 2:25

and one that can suffer the evil in meekness, and can inform them that resist - if that God at any time will give them repentance for to know the truth -

Hebrews 6:6

if they fall away, should be renewed again unto repentance: Forasmuch as they have, as concerning themselves, crucified the son of God afresh, making a mock of him.

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
And yet the LORD hath not given you a heart to perceive, nor eyes to see, nor ears to hear unto this day.
Isaiah 6:9
And so he said, "Go, and tell this people: 'Ye shall hear indeed, but ye shall not understand; ye shall plainly see, and not perceive.
Isaiah 44:18
Yet men neither consider nor understand; because their eyes are stopped that they cannot see, and their hearts, that they can not perceive.
Jeremiah 5:21
"Hear this, thou foolish and indiscreet people: ye have eyes, but ye see not; ears have ye, but ye hear not.
Matthew 13:14
And in them is fulfilled the prophecy of Isaiah, which prophecy saith, 'With the ears ye shall hear, and shall not understand; and with the eyes ye shall see, and shall not perceive."
Luke 8:10
And he said, "Unto you is it given to know the secrets of the kingdom of God: but to others in similitudes, that when they see, they should not see, and when they hear they should not understand.
John 12:37
And though he had done so many miracles before them, yet believed not they on him,
Acts 28:25
When they agreed not among themselves, they departed, after that Paul had spoken one word, "Well spake the holy ghost by Isaiah the prophet unto our fathers,
Romans 11:8
according as it is written, "God hath given them the spirit of unquietness: eyes that they should not see, and ears that they should not hear, even unto this day."

Be converted

Jeremiah 31:18
Moreover, I heard Ephraim, that was led away captive, complain on this manner, 'O LORD, thou hast corrected me, and thy chastening have I received, as an untamed calf. Convert thou me, and I shall be converted, for thou art my LORD God.
Ezekiel 18:27
And when a wicked turneth from his wickedness and doth justly and righteously, he shall save his soul:
Acts 3:19
Repent ye, therefore, and turn: that your sins may be done away when the time of refreshing cometh, which we shall have of the presence of the Lord,
2 Timothy 2:25
and one that can suffer the evil in meekness, and can inform them that resist - if that God at any time will give them repentance for to know the truth -
Hebrews 6:6
if they fall away, should be renewed again unto repentance: Forasmuch as they have, as concerning themselves, crucified the son of God afresh, making a mock of him.

General references

Proverbs 28:5
Wicked men discern not the thing that is right, but they that seek after the LORD, discuss all things.