"And He said, 'Do not lay your hand on the lad, or do anything to him; for now I know that you fear God, since you have not withheld your son, your only son, from Me.'" Genesis 22.12The LORD God tested Abraham's obedience. His response showed his fear. In other words, obedience is undeniable proof of faith and fear of God.
Whoever believes in God fears and obeys His Word; but whoever does not believe does not fear Him and therefore disobeys His Word.