Why do we need faith in order to know that something is sin?
Faith is necessary because sin is identified by what God says, not by human opinion. Unless a person believes God's Word about specific activities, they cannot recognize those acts as sin. When God speaks and one believes it, the reality of sin becomes known, guiding the daily walk.
Les explains that recognizing sin and dealing with sin comes down to one word: faith. Unless we can believe what God says about certain activities or certain acts, we do not know that it is sin. But when God says it and we believe it, then we know what it is. Faith guides us not only into salvation but all through our Christian experience, and it is all based on what the Book says, not what someone else says. Romans 3:23 says all have sinned and come short of the glory of God, and believing that about oneself is the first step. As people get into the Book and see what it says by faith, they take appropriate action.