From the moral reflections on Job by Pope St. Gregory the Great
Since the dawn goes from darkness into light, it is right that the Church of the elect should be called “dawn” or “first light.” As it is led from the night of disbelief into the light of faith, it is opened up to the splendour of heavenly brightness just as the dawn bursts into day after darkness. How right are the words of the Song of Songs: Who is she who is coming up like the dawn? The holy Church seeks the rewards of heavenly life and is rightly called the dawn because it deserts the shadows of sin and sparkles in the light of righteousness.
There is something subtler to learn from this, on considering the nature of the dawn. Dawn, or first light, proclaims that the night is over but does not yet manifest the full brightness of the day. It dispels night, it gives a beginning to the day, but still it is a mixture of light and darkness. All of us who follow the truth in this life, are we not exactly like the dawn? Some of the things we do are truly works of the light, but others are not entirely free of the remnants of darkness. No man is virtuous before you, says the psalmist, and again Scripture says we have all done wrong in many ways.
This is why Paul does not say “the night has passed and day has come,” but night has passed and day is approaching, showing beyond doubt that he is still in the dawn, after the end of darkness but still before rising of the sun.
The Church of the elect will be fully day only when the darkness of sin is no longer mixed in with it. It will be fully day only when it shines with the perfect warmth of a light that comes from within. God shows that we are still going through this dawn when he says to Job, Have you ever sent the dawn to its post? Something that is being sent somewhere is being sent from one place or state to another. What is the destined place of the dawn if not the perfect brightness of the eternal vision? And when it has reached its place, will it still have any of the darkness of the night that has passed? The dawn was intent on reaching its destined place when the psalmist said My soul thirsts for the living God; when shall I appear before the face of God? The dawn was hurrying to the place it knew to be its destiny when Paul said that he wanted to die and to be with Christ, and when he said For me to live is Christ and to die is gain.