By itself, hearing produces only transient impressions and momentary convictions of duty. The sincere Christian learns in order that he may do the will of God, not merely that he may know.

That is, considering attentively. Presumably, the person who looks into a mirror thereby gives evidence of a genuine desire to find out the facts. Similarly, “a hearer of the word” should seek, as a result of what he hears, to understand his spiritual condition. But this is not enough; he must do something about it.

 As a mirror reflects the likeness of the human face, soiled or blemished as it may be, so the law of God reveals the moral countenance, marred with defects and stained with sin. To hear and to understand the Word of God is like looking into a mirror. In viewing the perfect precepts of the law as magnified in the character of Jesus Christ, we become aware of our own shortcomings and defects. The mirror of truth never flatters. Paul was unaware of his own corrupt nature until he saw himself in the mirror of the law. Without the law he thought himself morally adequate, “alive,” but when he really understood its lofty principles he realized that he was spiritually dead (see on Rom. 7:9).

Or, “mirror.” Ancient mirrors were made of polished metal, not glass.