Jesus said that it is only when a believer has faith, that they can accomplish what God has for them:

 

© Photo Artist Susan Ruth Robertson 090025006100 038 - Copy.JPG
Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done.
Matthew 21:21