Hebrews 10:38

Now the just shall live by faith;

But if anyone draws back,

My soul has no pleasure in him.

We all know that if we believe we can do something we will.  The same concept applies to faith in God and His word.  If we believe in God and His word, then we will believe He can do it.  Drawing back from God is doubt, and God can’t work with doubt.  Faith is the door open to possibilities and doubts closes the door and locks it.