'Doubt' in the Bible

And immediately Jesus stretched out his hand and caught hold of him, and says to him, O thou of little faith, why didst thou doubt?

And Jesus answering said to them, Verily I say unto you, If ye have faith, and do not doubt, not only shall ye do what is done to the fig-tree, but even if ye should say to this mountain, Be thou taken away and be thou cast into the sea, it shall come to pass.

Verily I say to you, that whosoever shall say to this mountain, Be thou taken away and cast into the sea, and shall not doubt in his heart, but believe that what he says takes place, whatever he shall say shall come to pass for him.