'Have Faith' in the Bible

And Jesus said to them: Because of your unbelief. For verily I say to you, If you have faith like a grain of mustard-seed, you shall say to this mountain, Be removed from this place to that, and it shall be removed: and nothing shall be impossible for you.

Jesus answered and said to them: Verily I say to you, If you have faith, and doubt not, you shall do, not only what is done to the fig-tree, but even if you shall say to this mountain, Be taken up, and be thrown into the sea, it shall be done.