'Hardness' in the Bible

After looking around at them with anger and sorrow at the hardness of their hearts, He told the man, “Stretch out your hand.” So he stretched it out, and his hand was restored.

But Jesus told them, “He wrote this command for you because of the hardness of your hearts.

Later, He appeared to the Eleven themselves as they were reclining at the table. He rebuked their unbelief and hardness of heart, because they did not believe those who saw Him after He had been resurrected.