by St. Gregory the Theologian, excerpted from a homily (Festal Oration 38)  given by St. Gregory while Archbishop of Constantinople, on the Feast of the Nativity in the year 380.
Christ is born, give glory; Christ is from the heavens, go to meet Him; Christ is on earth, be lifted up. "Sing to the Lord, all the earth," and, to say both together, "Let the heavens be glad and let the earth rejoice," for the Heavenly One is now earthly. Christ is in the flesh, exult with trembling and joy; trembling because of sin, joy because of hope. Christ comes from a Virgin; women, practice virginity, that you may become mothers of Christ. Who would not worship the One "from the beginning"? Who would not glorify "the Last"?
Again the darkness is dissolved, again the light is established, again Egypt is punished by darkness. Again Israel is illumined by a pillar. Let the people siting in the darkness of ignorance see a great light of knowledge. "The old things have passed; behold, all things have become new." The letter withdraws, the spirit advances; the shadows have been surpassed, the truth has entered after them. Melchizedek is completed, the motherless One becomes fatherless; He was motherless first, fatherless second. The laws of nature are dissolved. The world above must be filled. Christ commands, let us not resist. "All nations, clap your hands," "for to us a Child is born, and to us a Son is given, the power is on His shoulder," for He is lifted up along with the cross, and He is called by the name "Angel of great counsel," that of the Father. Let John proclaim, "Prepare the way of the Lord." I myself will proclaim the power of this day. The fleshless One takes flesh, the Word is made coarse, the invisible One seen, the impalpable One is touched, the timeless One makes a beginning, the Son of God becomes a Son of Man, "Jesus Christ, the same yesterday and today and for the ages." Let Jews be scandalized, let Greeks mock, let heretics talk till their tongues ache. They will believe when they see Him ascend into heaven, and if not then, at least when they see Him coming from heaven and sitting as Judge.
These things come later. Now is the Feast of the Theophany, and so also of the Nativity; for it is called both, since the two names are ascribed to one reality. For God appeared to human beings through birth. On the one hand He is and is eternally from the eternal Being, above cause and principle, for there was not principle higher than the Principle. On the other hand for us He later comes into being, that the One who has given us being might also grant us well-being; or rather that, as we fell from well-being through evil, He might bring us back again to Himself through incarnation. The name is Theophany, since He has appeared, and Nativity, since He has been born.
This is our festival, this is the feast we celebrate today, in which God comes to live with human beings, that we may journey toward God, or return—for to speak thus is more exact—that laying aside the old human being we may be clothed with the new, and that as in Adam we have died so we may live in Christ, born with Christ and crucified with Him, buried with Him, and rising with Him. For it is necessary for me to undergo the good turnaround, and as painful things came from more pleasant things, so out of painful things more pleasant things must return. "For where sin abounded, grace superabounded," and if the taste of forbidden fruit condemned, how much more does the Passion of Christ justify? Therefore we celebrate the feast not like a pagan festival but in a godly manner, not in a worldly way but in a manner above the world. We celebrate not our own concerns but the One who is ours, or rather what concerns our Master, things pertaining not to sickness but to healing, not to the first shaping, but to the reshaping.
The Circumcision of Our Lord and Savior Jesus Christ and Commemoration of St. Basil the Great
Enthroned on high with the Eternal Father and Your divine Spirit, O Jesus, You willed to be born on earth of the unwedded handmaid, your Mother. Therefore You were circumcised as an eight-day old Child. Glory to Your most gracious counsel; glory to Your dispensation; glory to Your condescension, O only Lover of mankind.
Kontakion, Tone 3
The Lord of all accepts to be circumcised, thus, as He is good, excises the sins of mortal men. Today He grants the world salvation, while light-bearing Basil, high priest of our Creator, rejoices in heaven as a divine initiate of Christ.