'Doubt' in the Bible

But so that you may know that the Son of Man has the authority and power on earth to forgive sins”—He said to the paralyzed man,

I assure you and most solemnly say to you, whoever says to this mountain, ‘Be lifted up and thrown into the sea!’ and does not doubt in his heart [in God’s unlimited power], but believes that what he says is going to take place, it will be done for him [in accordance with God’s will].