John 12:40

"He has blinded their eyes and hardened their hearts, lest they should see with their eyes, and understand with their hearts and turn, so that I should heal them."

Romans 9:18-20

Therefore he has mercy on whom he wills, and he hardens the heart of whom he wills.

2 Thessalonians 2:11-12

For this reason God sends upon them a strong delusion so that they will believe what is false,

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 sends upon them a strong delusion so that they will believe what is false,

And hardened

John 12:40
"He has blinded their eyes and hardened their hearts, lest they should see with their eyes, and understand with their hearts and turn, so that I should heal them."
Romans 9:18
Therefore he has mercy on whom he wills, and he hardens the heart of whom he wills.