'Have Faith' in the Bible

And Jesus said unto them, Because of your unbelief: for verily I say unto you, If you have faith as a grain of mustard seed, you shall say unto this mountain, Remove from here to yonder place; and it shall remove; and nothing shall be impossible unto you.

Jesus answered and said unto them, Verily I say unto you, If you have faith, and doubt not, you shall not only do this which is done to the fig tree, but also if you shall say unto this mountain, Be removed, and be cast into the sea; it shall be done.