“That day is called the birthday of the Lord on which the Wisdom of God manifested Himself as a speechless Child and the Word of God wordlessly uttered the sound of a human voice.
His divinity, although hidden, was revealed by heavenly witness to the Magi and was announced to the shepherds by angelic voices.
With yearly ceremony, therefore, we celebrate this day which saw the fulfillment of the prophecy: ‘Truth is sprung out of the earth: and justice hath looked down from heaven.’ (Psalm 84:12)
Truth, eternally existing in the bosom of the Father, has sprung from the earth so that He might exist also in the bosom of a mother.
Truth, holding the world in place, has sprung from the earth so that He might be carried in the hands of a woman.
Truth, incorruptibly nourishing the happiness of the angels, has sprung from the earth in order to be fed by human milk.
Truth, whom the heavens cannot contain, has sprung from the earth so that He might be placed in a manger.
For whose benefit did such unparalleled greatness come in such lowliness? Certainly for no personal advantage, but definitely for our great good, if only we believe.
Arouse yourself, O man; for your God has become man. ‘Awake, sleeper, and arise from among the dead, and Christ will enlighten thee.’ (Eph. 5:14)
For you, I repeat, God has become man.
If He had not thus been born in time, you would have been dead for all eternity.
Never would you have been freed from sinful flesh, if He had not taken upon Himself the likeness of sinful flesh.
Everlasting misery would have engulfed you, if He had not taken this merciful form.
You would not have been restored to life, had He not submitted to your death; you would have fallen, had He not succored you; you would have perished, had He not come.
Let us joyfully celebrate the coming of our salvation and redemption. Let us celebrate the festal day on which the great and timeless One came from the great and timeless day to this brief span of our day.
He ‘has become for us righteousness, and sanctification, and redemption; so that, just as it is written, ‘Let him who boasts, boast in the Lord. (1 Cor. 1:30-31)'”
–Augustine of Hippo, “Sermon 185: On the Birthday of our Lord Jesus Christ,” Sermons on the Liturgical Seasons (ed. Hermigild Dressler; trans. Mary Sarah Muldowney; vol. 38; The Fathers of the Church; Washington, DC: The Catholic University of America Press, 1959), 38: 6-7.