Novatian, On the Trinity 24
The source of this heretical error, I believe, is their refusal to recognize any distinction between the Son of God and the son of man. They think that by erasing the difference, they can easily prove Jesus Christ to be both man and God. They want the son of man to be identical with the Son of God, so that the man, the flesh, and that fragile human substance may be declared the very Son of God. Since they will not separate the son of man from the Son of God, but instead vindicate the son of man as the Son of God, they end up asserting that Christ is only a man, yet the same as the Son of God. By this maneuver they try to set aside the testimony that "the Word became flesh and dwelt among us" (John 1:14), and that "you will call his name Emmanuel, which means God with us" (Matt 1:23).
They put forward and allege the words recorded in Luke's Gospel, trying to prove not what is true, but only what they wish to be true: "The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the holy one to be born will be called the Son of God" (Luke 1:35). "If," they argue, "the angel of God tells Mary that what is born of her is holy, then the substance of flesh and body comes from Mary. And this substance—that holy thing born of her—is proposed to be the Son of God. The man himself, they say, and that flesh of the body, that which is called holy, is the Son of God. Thus when Scripture says 'holy,' we are to understand Christ the son of man to be a man; and when it presents the Son of God, we are to perceive not God, but a man."
But divine Scripture easily convicts and exposes the heretics' frauds and thefts. If the text were merely: "The Spirit will come upon you, and the power of the Most High will overshadow you; therefore what is born of you will be called the Son of God," we might have needed another kind of argument against them, and would have had to seek other proofs and take up other weapons to overcome their snares and deceptions. But since Scripture itself, abundant with heavenly fullness, strips off the calumnies of these heretics, we rely confidently on what is written and overcome these errors without any doubt.
For the angel did not say, as we have already shown, merely "therefore what is born of you will be holy"; he added a conjunction: "therefore *and* what is born of you will be holy" (Luke 1:35). He did this to show that the holy thing born of her—that is, this substance of flesh and body—is *not primarily* the Son of God, but secondarily. Primarily, the Son of God is the Word of God incarnate through that Spirit of whom the angel speaks: "The Holy Spirit will come upon you, and the power of the Most High will overshadow you" (Luke 1:35). This is the true Son of God, who is from God. When he assumes this holy thing and joins the son of man to himself, drawing him up to himself, he grants and makes him the Son of God—which he was not by nature—so that the primacy of this divine name may reside in the Spirit of the Lord who descends and comes, while the sequence of the name belongs to the Son of God and man. Thus he deservedly *becomes* the Son of God, since he is not primarily the Son of God.
Therefore the angel, perceiving this arrangement and unfolding the order of this great mystery, did not confuse everything so as to leave no trace of distinction. Instead he marked a distinction, saying: "therefore *and* what will be born of you will be holy, and will be called the Son of God" (Luke 1:35). Had he not dispensed this distribution with its proper weights, but left it confused and mixed, he would have truly given the heretics grounds to declare that the son of man, insofar as he is man, is the same as the Son of God. But now, by expounding particularly, he has clearly expressed the order and reason of so great a sacrament, so as to say: "what is born of you will be holy, and will be called the Son of God"—proving that the Son of God descends. When he receives the son of man into himself, he consequently makes him the Son of God, because he associates and joins this son to himself, so that when the son of man adheres to the Son of God in birth, he may hold by this mixture what he could not possess by his own nature.
And so, by the angel's voice—what the heretics do not want—a distinction is made between the Son of God and the son of man, yet with their association, urging them to understand that Christ the son of man is a man, and also the Son of God; and that the man is the Word of God, who, as Scripture says, is God. Therefore they may know Christ Jesus the Lord to be composed and concreted from both, and in the concord of both substances, mutually bound by the interweaving of a reciprocal covenant, man and God—Scripture itself speaking this very thing with truth.
Latin
Sed erroris istius haereticorum inde, ut opinor, nata materia est, quia inter filium dei et filium hominis nihil arbitrantur interesse, ne facta distinctione et homo et deus Iesus Christus facile comprobetur. eundem enim atque ipsum, id est hominem filium hominis etiam filium dei, uolunt uideri, ut homo et caro et fragilis illa substantia eadem atque ipse filius dei esse dicatur; ex quo, dum distinctio filii hominis et filii dei nulla secernitur, sed ipse filius hominis dei filius uindicatur, homo tantummodo Christus idem atque filius dei asseratur. per quod nituntur excludere: uwerbum caro factum est et habitauit in nobis; et uocabitis nomen eius Emmanuel, quod est interpretatum nobiscum deus. Proponunt enim atque illa praetendunt, quae in euangelio Lucae relata sunt, ex quibus asserere conantur, non quod est, sed tantum illud quod uolunt esse: spiritus sanctus ueniet in te, et uirtus altissimi obumbrabit tibi; propterea et quod ex te nascetur sanctum, uocabitur filius dei. si ergo, inquiunt, angelus dei dicit ad Mariam, quod ex te nascetur sanctum, ex Maria est substantia carnis et corporis. hanc autem substantiam, id est sanctum hoc quod ex illa genitum est, filium dei esse proposuit. homo, inquiunt, ipse, et illa caro corporis, illud quod sanctum est dictum, ipsum est filius dei; ut et cum dicit scriptura sanctum, Christum filium hominis hominem intellegamus, et cum jiium dei proponit, non deum sed hominem percipere debeamus. Sed enim scriptura diuina haereticorum et fraudes et furta facile conuincit et detegit. si enim sic esset tantummodo: spiritus ueniet in te, et uirtus altissimi obumbrabit tibi; propterea quod nascetur ex te sanctum, uocabitur filius dei, fortasse alio esset nobis genere aduersus illos reluctandum, et alia nobis essent argumenta quaerenda et arma sumenda, quibus illorum et insidias et praestigias uinceremus. cum autem ipsa scriptura caelesti abundans plenitudine sese haereticorum istorum calumniis exuat, facile ipso quod scriptum est nitimur, et errores istos sine ulla dubitatione superamus. non enim dixit, ut iam expressimus, propterea quod ex te nascetur sanctum, sed adiecit coniunctionem: ait enim, propterea et quod ex te nascetur sanctum; ut illud ostenderet, non principaliter hoc sanctum, quod ex illa nascitur, id est istam carnis corporisque substantiam, filium dei esse, sed consequenter et in secundo loco: principaliter autem filium dei esse uerbum dei incarnatum per illum spiritum, de quo angelus refert: sf7zvitus ueniet in te, et uirtus altissimi obumbrabit tibi. Hic est enim legitimus dei filius, qui ex ipso deo est, qui dum Sanctum istud assumit et sibi filium hominis annectit et illum ad se rapit atque transducit, conexione sua et permixtione sociata praestat, et filium illum dei facit, quod ille naturaliter non fuit; ut principalitas nominis istius fs dei in spiritu sit domini, qui descendit et uenit; ut sequella nominis in filio dei et hominis sit, et merito consequenter hic filius dei factus sit, dum non principaliter filius dei est. atque ideo dispositionem istam angelus uidens et ordinem istum sacramenti expediens, non sic cuncta confundens ut nullum uestigium distinctionis collocarit, distinctionem posuit, dicendo: propterea et quod nascetur ex te sanctum, uocabitur filius dei: ne si distributionem istam cum libramentis suis non dispensasset, sed in confuso permixtam reliquisset, uere occasionem haereticis contulisset, ut hominis filium, qua homo est, eundem et dei et hominis filium pronuntiare deberent. nunc autem partiticulatim exponens, tam magni sacramenti ordinem atque rationem euidenter expressit, ut diceret, e quod ex te nascetur sanctum, uocabitur filius dei, probans quoniam filius dei descendit: qui dum filium hominis in se suscepit, consequenter illum filium dei fecit; quoniam illum filius sibi dei sociauit et iunxit, ut dum filius hominis adhaeret in natiuitate filio dei, ipsa permixtione feneratum et mutuatum teneret, quod ex natura propria possidere non posset. ac sic facta est angeli uoce, quod nolunt haeretici, inter filium dei hominisque, cum sua tamen sociatione, distinctio, urgendo illos uti Christum, hominis filium hominem, intellegant quoque dei filium, et hominem dei filium, id est dei uerbum (sicut scriptum est) deum, accipiant, atque ideo Christum Iesum dominum (ut ita dixerim) ex utroque contextum atque concretum, et in eadem utriusque substantiae concordia mutui ad inuicem foederis confibulatione sociatum, hominem et deum, scripturae hoc ipsum dicentis ueritate, cognoscant.