Unbelief is an evil heart, “Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God;”  Heb 3:12

And unbelief can put out a fire, “Now He did not do many mighty works there because of their unbelief.”  Mathew 15:38

When we ask for help, He is faithful, “…Lord, I believe; help my unbelief! ….He rebuked the unclean spirit, saying to it, “Deaf and dumb spirit, I command you, come out of him and enter him no more!”   Mark 9:24-25