Gregory_ThaumaturgusJust as from Adam was taken woman without his diminishing, so likewise from the Virgin was taken the body (Born of Her), wherein also the Virgin did not undergo diminishing, and Her virginity did not suffer harm.

Adam dwelt well and unharmed, when the rib was taken from him: and so without defilement dwelt the Virgin, when from Her was brought forth God the Word.

For this sort of reason particularly the Word assumed of the Virgin Her flesh and Her (corporeal) garb, so that He be not accounted innocent of the sin of Adam.

Since man stung by sin had become a vessel and instrument of evil, Christ took upon Himself this receptacle of sin into His Own flesh.

This was so that, the Creator having been co-united with the body, it should thus be freed from the foulness of the enemy, and man might thus be clothed in an eternal body, which might be neither perished nor destroyed for all eternity.

Moreover, He that is become the God-Man is born, not as ordinarily man is born—He is born as God made Man, manifest of this by His Own Divine power, since if He were born according to the general laws of nature, the Word would seem something imperfect.

Therefore, He was born of the Virgin and shone forth; therefore, having been born, He preserved unharmed the virginal womb, so that the hitherto unheard of manner of the Nativity should be for us a sign of great mystery.

[…] On this great day, now being celebrated, God has appeared as Man, as Pastor of the nation of Israel, Who has enlivened all the universe with His goodness.

O dear warriors, glorious champions for mankind, who did preach Bethlehem as a place of Theophany and the Nativity of the Son of God, who have made known to all the world the Lord of all, lying in a manger, and did point out God contained within a narrow cave!

And so, we now glorify joyfully a feast of the years. Just as hence the laws of feasts be new, so now also the laws of birth be wondrous.

On this great day now celebrated, of shattered chains, of Satan shamed, of all demons to flight, the all-destroying death is replaced by life, paradise is opened to the thief, curses are transformed into blessings, all sins are forgiven and evil is banished, truth is come.

[…] Traits pure and immaculate are implanted, virtue is exalted upon the earth, Angels are come together with people, and people make bold to converse with Angels.

Whence and why has all this happened? From this, that God has descended into the world and exalted mankind unto Heaven.

Gregory the Wonderworker (c.213-c.270): Discourse on the Nativity of Christ @ Orthodox Church in America [slightly adapted].