'Doubt' in the Bible

And Jesus answering said to them, 'Verily I say to you, If ye may have faith, and may not doubt, not only this of the fig-tree shall ye do, but even if to this mount ye may say, Be lifted up and be cast into the sea, it shall come to pass;

for verily I say to you, that whoever may say to this mount, Be taken up, and be cast into the sea, and may not doubt in his heart, but may believe that the things that he saith do come to pass, it shall be to him whatever he may say.

And they were all amazed, and were in doubt, saying one unto another, 'What would this wish to be?'

and I was wishing to be present with you now, and to change my voice, because I am in doubt about you.