Moses hadn’t been aware of it, but in his forty days of conversing with God, his face had taken on a marvelous brightness. Then, when he came down from the mountain he scared the people away because of the inhuman radiance of his face. To get the people back, he secured a veil around his ears. St. Peter’s has a statue of Moses wearing a marble veil.
St. Paul, writing to the Corinthians described something similar that happens with those who spend hours alone with God. Their souls take on a radiance.
The Church name for that radiance is Sanctifying Grace. It is an interior transformation taken on by those who advance from stage to stage in holiness. It results in one becoming more and more like God.
What Paul said in Chapter Three of his Second Letter to the Corinthians is, “And we, gazing with unveiled faces on God are being transformed from glory to glory into his image.”