Zeno of Verona (d. ca. 380), On the Birth of the Lord, II (= Tractatus VIII), translated from Patrologia Latina 11:412-415 by Andrew S. Jacobs. Please do not reproduce without permission.

I. Truly unexpected is the understanding of the hidden and venerable majesty, not to know God as God; and nothing should more fully be sought from him than that someone might know his will, without which one cannot serve him legitimately, nor be pleasing to him.  To wish for some other proposition to be imagined of God's foresight, through empty arguments about God, is not to worship but to be insane: especially if God, as the obstinant suppose, should be subject to a proposition; indeed, having for a short time removed the names of "Father" and "Son," you wouldn't know which one suffers injury, unless it is the case that both suffer, since the one name "God" is applied to both. So forget learning the two virgin births of our Lord Jesus Christ, Christian, lest you be deceived by error! One, which is not fitting for you to ask about, another, which legitimately, if you can, you are permitted to learn. So the first birth of our Lord remains only in the knowledge of the Father and Son, and has no sort of intermediary or witness, that out of the affection of the father's expression proceeded by a single agreement. But the second, which is carnal, is produced in multiple divine witnesses, so we find that it can be considered.

II. Indeed God who is the Son of God, at a designated time, his majesty set aside for a period, coming forth from his heavenly throne, measured out for himself an encampment in the preordinained Temple of the Virgin, in which in a hidden fashion he poured himself into a human being about to be born, and in that very place he mediated between that which he was and that which he was not. So being mixed with human flesh he formed himself into a child. Mary's proud belly burst out, not from a marital duty, but by faith; by the Word, not from seed. For ten months she did not experience nausea, as would be natural had she conceived a creature of the world in her: she gave birth not in pain, but in joy. Marvel at the matter: exulting, she brought forth a baby greater than the whole nature of antiquity. While pregnant the inexperienced girl did not groan. Not soiled, as is usually the case when the recumbent baby comes forth, it starts out spontaneously with the tears leading the way of crawling life. His mother was not exhausted by giving birth to such a weight, and she did not lie sick, pallid, with all her internal organs loosened. And the mother's Son was not smeared with any filth; nor indeed could he have anything really unclean around him, who had come to purify the human race of sins, filth, and stains. Then no purgings, which are dangerous at the end, were condemned to follow after the child from his mother's internal organs. No poultice, typical by custom, was applied to the pregnant virgin; indeed, brothers and sister, there could be no need of this for the woman who was deemed worthy to receive in her womb the Son, the Savior of all souls! O great mystery! Mary, incorrupt virgin, conceived; after conceiving she gave birth a virgin; and after giving birth she remained a virgin! The hand of the unbelieving midwife, testing the woman who just gave birth, burned as a witness of the virginity that she had discovered; when the baby touched it, that still devouring flame was stilled. So that happily curious healer, afterward marvelling at the virgin woman, marvelling at the child God, exulting with great joy, who came to treat him, withdrew having been treated. [1] So Christ had himself born a person, but could not born born like any old person. Then resplendent with his own light his whole body was borne without shadow; humble in flesh, but exalted by his omnipotent majesy. Who clearly then deemed it worthy to assume flesh, so that no one could, when the Day of Judgment comes, make an excuse for himself through flesh.