Lactantius, Divine Institutes 4.13

Therefore the highest God, the parent of all, decided to transfer his religion and so sent a teacher of justice from heaven, that he might give a new law to new worshipers in him or through him — not as he had done before through a man, yet still he willed him to be born as a man so that he might exist as wholly like the highest Father. For God the Father himself, the origin and principle of all things, lacks parents; therefore Trismegistus most truly names him ἀπάτωρ and ἀμήτωρ, because he was not generated by anyone. For this reason the Son also had to be born twice, that he himself might become ἀπάτωρ and ἀμήτωρ. In his first, spiritual birth he was ἀμήτωρ, because he was begotten by God the Father alone without a mother’s role; in his second, carnal birth he was ἀπάτωρ, because he was born from a virgin’s womb without a father’s role, so that, bearing a middle substance between God and man, he might lead this fragile, weak nature of ours by the hand toward immortality. He became the Son of God through the Spirit and the son of man through flesh — that is, both God and man. God’s power shone forth in him from the works he did; man’s frailty appeared in the passion he endured — why he undertook it I will explain shortly. Meanwhile, from the prophets we learn that he was both God and man, compounded of both natures. Isaiah testifies that he was God in these words: “Egypt has been exhausted, and the trade of the Ethiopians and the Sabeans, men of stature, will come over to you and become your servants; they will walk behind you in chains, they will worship you and pray to you, because God is in you, and there is no other God besides you. For you are God, though we did not know it, God of Israel, Savior. All who oppose you will be put to shame and will reverence you, and they will fall in confession” (Isaiah). Likewise Jeremiah says: “This is our God, and no other will be reckoned apart from him, who found every way of wisdom and gave it to Jacob his servant and to Israel his beloved. After these things he was seen on earth and conversed with men” (Jeremiah). Likewise David in Psalm 45: “Your throne, O God, endures forever and ever; the scepter of your kingdom is a scepter of equity. You loved justice and hated iniquity; therefore God, your God, has anointed you with the oil of gladness” (Psalm 45). By this word he also shows his name, since, as I taught above, he was called Christ from the anointing. Then Jeremiah teaches that the same one was a man, saying: “And he is a man — who can know him?” (Jeremiah). Likewise Isaiah: “And the Lord will send them a man who will save them, and judging will heal them” (Isaiah).