In Luke 4:4 Jesus tells the Devil, in response to the first of his temptations, "It is written: 'Man shall not live by bread alone, but by every word of God.'" This is not some general statement that allows us to choose what we will and will not obey, but a requirement for each of us, to the best of our ability, to follow every word of God in living our lives before Him. To do this takes real faith. God has given us "the way of righteousness," a revelation the most people just cannot comprehend, and He is looking for evidence that we not only assent to it but are also living it.
It is the works of obedience that change us, that reflect that we are striving to live as God lives. This is what God counts as proper evidence of our faith. In James 2:17, 20, 26, he tells us that, without works, our faith is dead, and these works are defined as putting into practice the instructions of God in our lives like Abraham did.
When God saw Abraham's obedience. He said, "Now I know that you fear Me!"
God should be able to say that about each of us.. Do we have the faith to live by every word of God?