'Unbelief' in the Bible

And he wondered because of their unbelief. And he went round the villages in a circuit, teaching.

And immediately the father of the young child crying out said with tears, I believe, help mine unbelief.

Afterwards as they lay at table he was manifested to the eleven, and reproached them with their unbelief and hardness of heart, because they had not believed those who had seen him risen.