'Doubt' in the Bible

And immediately Jesus extended his hand [and] caught him and said to him, "[You] of little faith! Why did you doubt?"

And Jesus answered [and] said to them, "Truly I say to you, if you have faith and do not doubt, you will do not only [what was done to] the fig tree, but even if you say to this mountain, 'Be lifted up and thrown into the sea," it will happen!