The church is the sun and the moon and the stars, to which it was said, “Fair as the moon, bright as the sun.” By it our Joseph is adored in this world as in Egypt, when he is raised from humble to high estate.
“As beautiful as the special moon.” The experts in these matters say the moon gets its light from the sun’s rays and gets partial light when a small part of it faces the sun. When it is directly opposite and is in full view of the sun, it is completely lit up as though reflecting its face like a kind of mirror and leaving no part of its bulk unlit. The church of Christ likewise, therefore, the congregation of the souls made perfect in virtue, “with unveiled face seeing the glory of the Lord as though reflected in a mirror,” in the words of blessed Paul, “is being transformed into the same image from one degree of glory to another, as a work of the Lord, the Spirit.” And it becomes so completely luminous as to resemble a moon, and a “special moon,” that is, full moon.
The bride, however, is not only “like a special moon,” but also she will shine in the future life “like a sun,” astounding all with its brightness. They will marvel not only at her light but also at her orderliness. There is nothing disordered about the Lord’s bride, nothing undetermined; she gives practical directions like a kind of plumb line, and regulates her own life by use of norm and rule.
By clinging continually to God the Word, she is made wholly on fire, like a burning coal. Also like a burning coal among a number of dead coals, when joined to the others, she ignites them all. Thus, in the midst of the souls of the dead [destined] for eternal life, she alone, the singular chosen one, vivifies all souls who believe in her, makes them like herself, and draws them to her beauty. Nevertheless, uniquely splendid like the moon, perfect in heaven among the stars, she in their midst is proven to glow with everlasting beauty more than all others. Chosen like the sun in paternal majesty among all the powers of the heavenly hosts, she is proclaimed as one to be admired by all, as the following verse teaches: “The maidens saw her and called her most blessed; queens and concubines also praised her.”
You are rightly compared with this figure since you raise your precious head over all races, and you transmit the souls of the just like resplendent stars to the kingdom above. You are a pyramid full of heavenly corn, the blessed gathering of saintly people from diverse nations, the shining assembly of bright minds, a structure that cannot be dismantled since it is fashioned from living stones, the eternal happiness of all who are blessed, brighter than the sun, whiter than snow, without spot or wrinkle. Of you it is written in the Song of Songs: “Who is she that comes forth as the morning rising, fair as the moon, bright as the sun, terrible as an army set in array?” - "Exposition of the Psalms, Preface 17"
You are properly compared to this figure since you raise up your precious head from all the nations, and you conduct the souls of the just, like exceptional lights to the kingdom above. You are a pyramid filled with heavenly corn, the blessed gathering of saints from many nations, a bright assembly of clear minds, an indestructible building made of living stones, the eternal happiness of all the blessed, brighter than the sun, whiter than snow, without stain, without wrinkle. It is written about you in Song of Songs: “Who is she who comes forth, rising like the dawn, beautiful as the moon, as exceptional as the sun, terrible as an army arrayed for battle?”
Who is this that comes forth, etc. Therefore, this Synagogue, converted to the faith of Christ, speaks, marveling at the Church being exalted by divine grace so much that it cannot be overcome by any powers of the worldly empire, even though it is very humble. "Who comes forth," it says, because it did not stand in one place, did not appear for a short time, but extended its faith and fame over the whole world, and throughout the ages of the passing world, it does not cease striving for the crown of eternal life. It comes forth, however, as the dawn rising, because the rise of true light in it, after the darkness of ignorance, is shown far to the world, as its heralds are admonishing and saying that the night has passed, but the day has approached. Let us therefore cast off the works of darkness, and put on the armor of light, and so on (Rom. XIII).
Beautiful as the moon, chosen as the sun, etc. Beautiful as the moon, because illuminated by the Sun of righteousness, it passes through the night of this world, and floods it with the light of heavenly knowledge and evangelical way of life; chosen as the sun, because it receives the image of its same Creator and illuminator in itself, walking in all righteousness, holiness, and truth, and truly giving thanks to Him, because the light of Your face, Lord, has been signed upon us (Psalm IV). Also beautiful as the moon, in the night of present life, where, with the varying state of times, now bright to the world, now despised and oppressed; now full of the brilliance of virtues, now disfigured by the vices of the wicked, it imitates in many ways the path of the moon increasing and waning. Chosen as the sun, in the day of future blessedness, where, with the state of eternity remaining, it will shine with the true vision of unchangeable light, fulfilled by His promise, in which it is said: The righteous will shine like the sun in the kingdom of their Father (Cant. VI). Terrible as an army set in array, because it could never be restrained by any clouds of adversity, without showing in itself the beauty of both the moon and the sun: namely, the moon, in the laborious light of good action in the meantime; the sun, in the hope of eternal blessed recompense. And well terrible as an army set in array, because the more perfectly it places the order of virtues in itself, the more terrible it is to the aerial powers, and the whole Church and every faithful soul stands: for in certain good deeds, for example, vigils, fasts, manual labor, meditation on Scriptures, the word of preaching, modest silence, whoever does not know how to hold necessary order, errs. For these and many other such things, as they are often held usefully, so also they are sometimes healthfully interrupted for a time. But there are more excellent gifts of virtues, without which one cannot attain life, such as faith, hope, and charity; which ought therefore never by any consideration of time or place to be absent from the hearts of admonishing faithful. Therefore, whatever soul continually fortifies itself with more eminent virtues, and also diligently girds itself for the exercise of lesser ones, where place and hour are fitting, this is terrible to all adversaries as an army set wisely and firmly in order proceeds. This while a few followers of the Jews believe and worthily admire the struggles of the Church, she herself agrees with the one praising and immediately indicates the reason for her military preparations, responding with the voice of the doctors, that is, leaders of her spiritual militia.
[AD 430] Augustine of Hippo on Song of Solomon 6:10