When the devil tempted Jesus to turn rocks into bread, our Savior responded with “Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God.” (Matt 4:4). Therefore, we must live by every word of God. But, in order to do this, we must have every word of God. How do we know that we have every word of God today? We know this because God has promised to preserve them for us.
First, remember that the Word of God was inspired directly by God.