James 1:23-25 For if any be a hearer of the word, and not a doer, he is like unto a man beholding his natural face in a glass: For he beholdeth himself, and goeth his way, and straightway forgetteth what manner of man he was. But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed.
First, James is speaking to Christians only. This is not for the unsaved.
Secondly, the word "glass" is the Old English word meaning "mirror."
Hear James likens God's Word to a mirror. It is a foolish man who looks into the mirror in the morning, combs his hair, brushes his teeth, etc., and then walks away and forgets what he has done (what he looks like--hair combed?)
It is a foolish man who reads God's Word and cannot apply it to himself. The Word of God is like a mirror reflecting ourselves, our image right back at us. The more we read it, the more we see of our own sinful selves. It tells us of our sin. The closer we draw nigh to God through the Word, the more we see the sin. The brighter the light in the bathroom, the easier it is to see the blemishes on your face as you look in the mirror. So it is in the Word of God, as it reflects those sins right back at you. God reveals our sins through His Word. If we can't see them then we are not reading His Word very much, or are not spending much time with him.