'Unbelief' in the Bible

And He wondered at their unbelief.And He was going around the villages teaching.

Immediately the boy’s father cried out and said, “I do believe; help my unbelief.”

Afterward He appeared to the eleven themselves as they were reclining at the table; and He reproached them for their unbelief and hardness of heart, because they had not believed those who had seen Him after He had risen.