Romans 9:18

So then He hath mercy on whom He pleaseth, and whom He will, He hardeneth.

John 12:40

He hath blinded their eyes, and hardened their heart, that they might not see with their eyes, and understand with their heart, and be converted, and I should heal them.

Romans 1:28

And as they were not careful to acknowledge God, God gave them up to an undiscerning mind to do things that were not fit to be done:

Romans 11:8-10

(according as it is written, God hath given them a spirit of slumber, that their eyes could not see and their ears could not hear,) even unto this day.

2 Corinthians 2:16

to these indeed we are an odor of death to death; to those an odor of life unto life. And who is sufficient for these things?

2 Thessalonians 2:10-12

and wonders, and with all iniquitous fraud, among those that shall perish; because they received not the love of the truth, by which they might be saved.

1 Peter 2:8

and a stone of stumbling, and a rock of offence. These stumble at the word through unbelief, unto which also they 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, that they might not see with their eyes, and understand with their heart, and be converted, and I should heal them.
Romans 1:28
And as they were not careful to acknowledge God, God gave them up to an undiscerning mind to do things that were not fit to be done:
Romans 9:18
So then He hath mercy on whom He pleaseth, and whom He will, He hardeneth.
Romans 11:8
(according as it is written, God hath given them a spirit of slumber, that their eyes could not see and their ears could not hear,) even unto this day.
2 Corinthians 2:16
to these indeed we are an odor of death to death; to those an odor of life unto life. And who is sufficient for these things?
2 Thessalonians 2:10
and wonders, and with all iniquitous fraud, among those that shall perish; because they received not the love of the truth, by which they might be saved.
1 Peter 2:8
and a stone of stumbling, and a rock of offence. These stumble at the word through unbelief, unto which also they were appointed.