Mark 4:12

So that seeing they may see, and it will not be clear to them; and hearing it, they will not get the sense; for fear that they may be turned again to me and have forgiveness.

Isaiah 6:9-10

And he said, Go, and say to this people, You will go on hearing, but learning nothing; you will go on seeing, but without getting wiser.

Jeremiah 5:21

Give ear now to this, O foolish people without sense; who have eyes but see nothing, and ears without the power of hearing:

Deuteronomy 29:4

But even to this day the Lord has not given you a mind open to knowledge, or seeing eyes or hearing ears.

Jeremiah 31:18-20

Certainly Ephraim's words of grief have come to my ears, You have given me training and I have undergone it like a young cow unused to the yoke: let me be turned and come back, for you are the Lord my God.

Matthew 13:14-15

And for them the words of Isaiah have come true, Though you give ear, you will not get knowledge; and seeing, you will see, but the sense will not be clear to you:

Luke 8:10

And he said, To you is given knowledge of the secrets of the kingdom of God; but to the others, they are given in stories, so that seeing, they may not see, and though they give hearing, the sense will not be clear to them.

Isaiah 44:18

They have no knowledge or wisdom; for he has put a veil over their eyes, so that they may not see; and on their hearts, so that they may not give attention.

Ezekiel 12:2

Son of man, you are living among an uncontrolled people, who have eyes to see but see not, and ears for hearing but they do not give ear; for they are an uncontrolled people.

Ezekiel 18:27-32

Again, when the evil-doer, turning away from the evil he has done, does what is ordered and right, he will have life for his soul.

John 12:37-41

But though he had done such a number of signs before them, they still had no belief in him:

Acts 3:19

So then, let your hearts be changed and be turned to God, so that your sins may be completely taken away, and times of blessing may come from the Lord;

Acts 28:25-27

And they went away, for there was a division among them after Paul had said this one thing: Well did the Holy Spirit say by the prophet Isaiah to your fathers,

Romans 11:8-10

As it was said in the holy Writings, God gave them a spirit of sleep, eyes which might not see, and ears which have no hearing, to this day.

2 Timothy 2:25

Gently guiding those who go against the teaching; if by chance God may give them a change of heart and true knowledge,

Hebrews 6:6

And then let themselves be turned away, it is not possible for their hearts to be made new a second time; because they themselves put the Son of God on the cross again, openly shaming 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
But even to this day the Lord has not given you a mind open to knowledge, or seeing eyes or hearing ears.
Isaiah 6:9
And he said, Go, and say to this people, You will go on hearing, but learning nothing; you will go on seeing, but without getting wiser.
Isaiah 44:18
They have no knowledge or wisdom; for he has put a veil over their eyes, so that they may not see; and on their hearts, so that they may not give attention.
Jeremiah 5:21
Give ear now to this, O foolish people without sense; who have eyes but see nothing, and ears without the power of hearing:
Matthew 13:14
And for them the words of Isaiah have come true, Though you give ear, you will not get knowledge; and seeing, you will see, but the sense will not be clear to you:
Luke 8:10
And he said, To you is given knowledge of the secrets of the kingdom of God; but to the others, they are given in stories, so that seeing, they may not see, and though they give hearing, the sense will not be clear to them.
John 12:37
But though he had done such a number of signs before them, they still had no belief in him:
Acts 28:25
And they went away, for there was a division among them after Paul had said this one thing: Well did the Holy Spirit say by the prophet Isaiah to your fathers,
Romans 11:8
As it was said in the holy Writings, God gave them a spirit of sleep, eyes which might not see, and ears which have no hearing, to this day.

Be converted

Jeremiah 31:18
Certainly Ephraim's words of grief have come to my ears, You have given me training and I have undergone it like a young cow unused to the yoke: let me be turned and come back, for you are the Lord my God.
Ezekiel 18:27
Again, when the evil-doer, turning away from the evil he has done, does what is ordered and right, he will have life for his soul.
Acts 3:19
So then, let your hearts be changed and be turned to God, so that your sins may be completely taken away, and times of blessing may come from the Lord;
2 Timothy 2:25
Gently guiding those who go against the teaching; if by chance God may give them a change of heart and true knowledge,
Hebrews 6:6
And then let themselves be turned away, it is not possible for their hearts to be made new a second time; because they themselves put the Son of God on the cross again, openly shaming him.

General references

Proverbs 28:5
Evil men have no knowledge of what is right; but those who go after the Lord have knowledge of all things.

Basic English, produced by Mr C. K. Ogden of the Orthological Institute - public domain