Romans 9:18

Then therefore he has mercy on whom he will, and whom he will he hardens.

John 12:40

He hath blinded their eyes, and hardened their heart; in order that they may not see with their eyes, nor understand with their heart, and turn, and I shall heal them.

Romans 1:28

And as they did not approve to have God in their knowledge, God gave them up to a reprobate mind, to do those things which are inappropriate;

Romans 11:8-10

as has been written, God has given them the spirit of slumber, eyes that they should not see, and ears that they should not hear, unto this day.

2 Corinthians 2:16

unto the latter a savour from death unto death; but unto the former a savour from life unto life. And who is sufficient for these things?

2 Thessalonians 2:10-12

and in all the deception of unrighteousness to those who perish; because they did not receive the divine love of the truth, that they might be saved.

1 Peter 2:8

who stumble over the word, disbelieving: unto which they indeed were appointed.

Treasury of Scripture Knowledge

Summary

And the LORD said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go.

Bible References

I will harden

John 12:40
He hath blinded their eyes, and hardened their heart; in order that they may not see with their eyes, nor understand with their heart, and turn, and I shall heal them.
Romans 1:28
And as they did not approve to have God in their knowledge, God gave them up to a reprobate mind, to do those things which are inappropriate;
Romans 9:18
Then therefore he has mercy on whom he will, and whom he will he hardens.
Romans 11:8
as has been written, God has given them the spirit of slumber, eyes that they should not see, and ears that they should not hear, unto this day.
2 Corinthians 2:16
unto the latter a savour from death unto death; but unto the former a savour from life unto life. And who is sufficient for these things?
2 Thessalonians 2:10
and in all the deception of unrighteousness to those who perish; because they did not receive the divine love of the truth, that they might be saved.
1 Peter 2:8
who stumble over the word, disbelieving: unto which they indeed were appointed.