"Out of the abundance of the heart the mouth speaketh. A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things." (Matthew 12:34-35)
Words won't work without faith any more than faith will work without words! It takes them both to put the law of faith in motion.
Many believers don't realize that. They'll continually speak words of doubt and unbelief, then they'll jump up one day and say a couple of faith words and expect mountains to move-- and to their dismay, they don't.
Why not?
Because as Matthew 12:34-35 says, it's the words that come from the heart that produce results. The person who just throws in a couple of faith words now and then isn't speaking them from the abundance of his heart, so they're not effective.
Does that mean you shouldn't start speaking words of faith until you're sure you have the faith to back them?