Those under the new covenant behold God’s glory even more plainly than Moses could (Ex 33:20); thus, like Moses, they are transformed to reflect God’s glory by the Spirit. On the “mirror.”
The mirrors of antiquity were flat disks cast from bronze (Job 37:18; Ex 38:8) and then polished to be as reflective as possible. In 1 Corinthians 13:12 Paul contrasts the earthly and heavenly knowledge of God: “Now we see but a poor reflection [Gk ainigma ”riddle,“ ”intimation“] as in a mirror; then we shall see face to face” (NIV).
Since mirrors of Paul’s day did not yield the bright, clear images that silvered glass does, many have plausibly interpreted the words to refer to the inferior quality of the image. Alternatively, this enigmatic metaphor expresses not the inferior qualities of a mirror but rather that what appears in the mirror is only an indirect reflection of the viewed object, which is perplexing and requires interpretation.
Paul asserts that the Christian can only see and understand God through secondary means. In the heavenly state intermediary means, such as human expressions of love (1 Cor 13) or Scripture itself (Jas 1:25), will not be necessary, for we shall see God “face to face.” Paul further enhances the mirror metaphor by comparing partial and full knowledge. God already fully knows the Christian, but Christians do not know God in full. One day all believers accepted into the heavenly kingdom will have their knowledge completed. Until that day, mirror reflections of reality are an imperfect means of understanding the riddle (Gk. ainigma) of life.
Although the word mirror does not appear in 2 Corinthians 3:18, by using the Greek verb katoptrizō, “to look at something as in a mirror,” Paul takes the mirror metaphor one step further into the Christian spiritual life. Here the veiling of Moses’ glory after receiving the law (Ex 34:33) is contrasted to the unveiling of the Christian’s heart and mind to reflect the liberating work of Jesus Christ. With an unveiled mind the Christian is able to be more like Christ and so reflect the glory of God to others. In effect, Christians have the freedom and the privilege to be mirror metaphors for the virtues of Jesus Christ. We are not only imitators of those who imitate Christ (1 Cor 4:16; 11:1; 1 Thess 1:6; Heb 6:12), but direct reflectors of Christ. Those who peer into us must see Jesus.
Finally, in James 1:23–25 the writer compares the oblivious hearer of God’s message to one who glances at a mirror and then instantly forgets the personal image, neglecting to tidy up or to improve oneself. The law, like a mirror, shows us our true selves. But what benefit is that if we fail to act on what we learn? In context, the Word of God is also part of the mirror metaphor. “But the man who looks intently into the perfect law that gives freedom,” (Jas 1:25 NIV) presents the Scriptures as an efficacious mirror for blessing-if, that is, the Christian does not forget what he has read or seen or heard.