One of the church's earliest and best Christmas sermons was preached by Gregory of Nazianzus (A.D. 329-389) in Constantinople's Church of the Resurrection on December 25, A.D. 380. A well-educated man from Cappadocia, Gregory's life alternated between monasticism and pressure into public ministry—eventually into the bishopric of Constantinople (which he resigned shortly after his appointment). A defender of orthodoxy against the Arians (who believed Jesus was not fully God), Gregory also condemned the emperor Julian, a pagan, for attempting to exclude Christians from higher learning. But in his love for learning, Gregory also believed that belief in God's incomprehensibility was a necessary element of orthodox theology. For his rhetorical skill, especially against the Arians, he was given the title "the theologian."

Christ is born, glorify ye Him. Christ from heaven, go ye out to meet Him. Christ on earth; be ye exalted. Christ in the flesh, rejoice with trembling and with joy; with trembling because of your sins, with joy because of your hope. Christ of a Virgin, without Mother, becomes without Father (without Mother of His former state, without Father of His second). He Who is not carnal is Incarnate; the Son of God becomes the Son of Man.

The Festival is the Theophany or Birthday, for it is called both, two titles being given to the one thing. For God was manifested to many by birth. On the one hand Being, and eternally Being, of the Eternal Being, above cause and word, for there was no word before The Word; and on the other hand for our sakes also Becoming, that He Who gives us our being might also give us our Well-being, or rather might restore us by His Incarnation, when we had by wickedness fallen from well-being. The ...