Mark 4:12

so that, "for all their looking they may not see, and for all their hearing, they may not understand, lest perchance they should turn and be pardoned.

Matthew 13:14-15

And in them is being fulfilled that prophecy of Isaiah which says. "Hearing you will hear and not understand; Seeing you will see and not perceive;

Luke 8:10

He answered. "To you it is given to understand the mysteries of the kingdom of God; But all others are taught in parables so that seeing they shall not see, and hearing they shall not hear.

John 12:37-41

With these words Jesus went away and hid himself from them. But although he had wrought such signs in their presence, still they did not believe in him.

Acts 3:19

"Repent then! and reform, from the blotting out of your sins, so that there may come times of refreshing from the presence of the Lord;

Acts 28:25-27

Unable to agree among themselves, they began to go, but not before Paul had spoken a word to them, saying. "Right well did the Holy Spirit say to your ancestors, through the prophet Isaiah.

Romans 11:8-10

According as it is written, God has given them a spirit of slumber, Eyes that they should not see, Ears that they should not hear, unto this day.

2 Timothy 2:25

He must be gentle when instructing opponents; for possibly God may give them a change of mind for the recognition of the truth,

Hebrews 6:6

and then fallen away, it is impossible to renew them again unto repentance. For they repeatedly crucify to themselves the Son of God afresh, and expose 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.

Bible References

That seeing

Matthew 13:14
And in them is being fulfilled that prophecy of Isaiah which says. "Hearing you will hear and not understand; Seeing you will see and not perceive;
Luke 8:10
He answered. "To you it is given to understand the mysteries of the kingdom of God; But all others are taught in parables so that seeing they shall not see, and hearing they shall not hear.
John 12:37
With these words Jesus went away and hid himself from them. But although he had wrought such signs in their presence, still they did not believe in him.
Acts 28:25
Unable to agree among themselves, they began to go, but not before Paul had spoken a word to them, saying. "Right well did the Holy Spirit say to your ancestors, through the prophet Isaiah.
Romans 11:8
According as it is written, God has given them a spirit of slumber, Eyes that they should not see, Ears that they should not hear, unto this day.

Be converted

Acts 3:19
"Repent then! and reform, from the blotting out of your sins, so that there may come times of refreshing from the presence of the Lord;
2 Timothy 2:25
He must be gentle when instructing opponents; for possibly God may give them a change of mind for the recognition of the truth,
Hebrews 6:6
and then fallen away, it is impossible to renew them again unto repentance. For they repeatedly crucify to themselves the Son of God afresh, and expose him to an open shame.