John 12:40

He hath blinded their eyes and make their hearts hard, Lest they should see with their eyes, perceive with their minds, And should turn, and I should heal them.

Romans 9:18-20

So then he has mercy on whom he will, and whom he will, he hardens.

2 Thessalonians 2:11-12

For this reason God is sending on them an energy of delusion, that they should put faith in a falsehood;

Treasury of Scripture Knowledge

Summary

O LORD, why hast thou made us to err from thy ways, and hardened our heart from thy fear? Return for thy servants' sake, the tribes of thine inheritance.

And hardened

Bible References

Why

2 Thessalonians 2:11
For this reason God is sending on them an energy of delusion, that they should put faith in a falsehood;

And hardened

John 12:40
He hath blinded their eyes and make their hearts hard, Lest they should see with their eyes, perceive with their minds, And should turn, and I should heal them.
Romans 9:18
So then he has mercy on whom he will, and whom he will, he hardens.