'Hardened' in the Bible

because they did not understand about the loaves, but their hearts were hardened.

When he learned of this, Jesus said to them, "Why are you arguing about having no bread? Do you still not see or understand? Have your hearts been hardened?

"He has blinded their eyes and hardened their heart, so that they would not see with their eyes and understand with their heart, and turn to me, and I would heal them."

What then? Israel failed to obtain what it was diligently seeking, but the elect obtained it. The rest were hardened,

But exhort one another each day, as long as it is called "Today," that none of you may become hardened by sin's deception.