“With unveiled face, beholding as in a mirror the glory of the Lord, we are all being transformed into the same image [Greek: icon], from glory to glory, and this is from the Lord, the Spirit. . . . Even if our Good News is veiled, it is veiled in those who perish, as the god of this world has blinded the minds of those who do not believe, so that the light of the Good News of the glory of Christ who is the image [Greek: icon] of God should not dawn on them.” (2 Corinthians 3:18, 4:3-4, EOB)
This transformation of all believers into the likeness of Christ (cf. “the same image” [2 Corinthians 3:18] and “Christ who is the image of God [4:4] – the key word eikon is used in both places) should be understood as a further clarification of the senses in which Paul can claim that the Corinthians are a letter from Christ that can be known and read by everyone. Because they are being changed into the likeness of Christ, they manifest the life of Jesus in their mortal flesh (cf. 2 Cor. 4:11). Consequently, the deepest paradox of the passage emerges: Paul’s reading of the sacred text (Exodus 34) reveals that revelation occurs not primarily in the sacred text but in the transformed community of readers.
(Richard B. Hays, Echoes of Scripture in the Letters of Paul, p. 144)
As St. Paul states it Jesus Christ is the image (icon) of God the Father and we believers are being transformed into that same image! We believers are becoming Christ. We are the Church (1 Corinthians 12:27), the Church is the Body of Christ (Colossians 1:18), and so we together are becoming Christ. We are being transformed by the Holy Spirit into Christ – not individually, but collectively as part of the Church which is Christ’s body. In as much as we become the image of God, in as much as we become Christ, we become the Word of God to the world. To read and understand Scripture, we need to be able to see Christ manifested in the world – we need to see the Church. The Church is to be light to the world thus fulfilling Christ’s own teaching. We are to be the fullness of Christ in the world. As Richard Hayes notes above for people to understand a passage such as Exodus 34 they need to see Christ, visible to them in His Body, the Church.