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 9:18-20

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

2 Thessalonians 2:11-12

And for this cause God will send upon them the efficacy of error, so that they shall themselves believe the lie:

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
And for this cause God will send upon them the efficacy of error, so that they shall themselves believe the lie:

And hardened

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 9:18
So then He hath mercy on whom He pleaseth, and whom He will, He hardeneth.