'Have Faith' in the Bible

And Jesus said to them, Because of your unbelief. For verily I say to you, If ye have faith as a grain of mustardseed, ye shall say to this mountain, Remove hence to yonder place, and it shall remove, and nothing shall be impossible to you.

Jesus answering said to them, Verily I say to you, if ye have faith and doubt not, ye shall not only do this to the fig-tree, but also if ye shall say to this mountain, Be thou lifted up, and be thou cast into the sea; it shall be done.