18 Now the birth of Jesus Christ took place in this way. When his mother Mary had been betrothed to Joseph, before they came together she was found to be with child from the Holy Spirit. 19 And her husband Joseph, being a just man and unwilling to put her to shame, resolved to divorce her quietly. 20 But as he considered these things, behold, an angel of the Lord appeared to him in a dream, saying, “Joseph, son of David, do not fear to take Mary as your wife, for that which is conceived in her is from the Holy Spirit. 21 She will bear a son, and you shall call his name Jesus, for he will save his people from their sins.” 22 All this took place to fulfill what the Lord had spoken by the prophet:
23 “Behold, the virgin shall conceive and bear a son,
and they shall call his name Immanuel”
(which means, God with us). 24 When Joseph woke from sleep, he did as the angel of the Lord commanded him: he took his wife, 25 but knew her not until she had given birth to a son. And he called his name Jesus. (Matthew 1:18-25)
His Corporeal Birth and His Divinity - Chromatius of Aquileia
John, however, addresses the issue of Jesus' divine birth in the preface to his Gospel: "In the beginning was the Word, and the Word was with God, and God was the Word. This was with God in the beginning. And all things were made through him and without him nothing was made." The Evangelists help us to recognize both the divine and corporeal birth of the Lord, which they describe as a twofold mystery and a kind of double path. Indeed, both the divine and the bodily birth of the Lord are indescribable, but that from the Father vastly exceeds every means of description and wonder. The bodily birth of Christ was in time; his divine birth was before time. The one in this age, the other before the ages. The one from a virgin mother, the other from God the Father. Angels and men stood as witnesses at the corporeal birth of the Lord, yet at his divine birth there was not witness except the Father and the Son, because nothing existed before the Father and the Son. But because the Word could not be seen as God in the glory of his own divinity, he assumed visible flesh to demonstrate his invisible divinity. He took from us what is ours in order to give generously what is his. Tractate on Matthew 2.1.