'Have Faith' in the Bible

And he says to them, Because of your unbelief; for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say to this mountain, Be transported hence there, and it shall transport itself; and nothing shall be impossible to you.

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.