Faith is the Substance
Faith is the substance of things hoped for, the evidence of things not seen.
Hebrews 11:1
Faith in God is a real, active, and living thing. God is alive, and powerful. Faith sees Him, and the word of His power overcomes what cannot be otherwise overcome, and carries a person with it through otherwise impossible situations.
It was by faith in God that David conquered the giant, and it was by faith in God that Jonathan, his friend, along with his armor bearer, single-handedly took on an entire Philistine garrison. It was by faith that overcame their weaknesses and came to be firmly established in the land.