Justin Martyr, First Apology 33
Once more, He was foretold through Isaiah to be born of a virgin, just as He Himself spoke it: 'Behold, the virgin will conceive and bear a son, and they will call his name Immanuel,' which means, 'God with us' (Isaiah 7:14). God declared through the prophetic Spirit those things that human beings considered unbelievable and impossible, so that when they came to pass they would not be dismissed but believed precisely because they had been foretold. We must now clarify the meaning of the prophecy, lest anyone who fails to grasp it accuse us of the very thing we charged against the poets when they claimed that Zeus visited women for the sake of lust. The statement 'the virgin will conceive' signifies that she conceived without sexual union; if she had lain with any man she would no longer have been a virgin. Instead, the power of God came upon her and overshadowed her, making her pregnant while she remained a virgin. The angel sent to her at that time announced the good news: 'Behold, you will conceive in your womb by the Holy Spirit and bear a son, and he will be called the Son of the Most High, and you shall call his name Jesus, for he will save his people from their sins.' Those who remembered every detail concerning our Savior Jesus Christ taught this, and we believed them, because the prophetic Spirit had already declared through Isaiah that He would be born in this manner, just as we have shown. The Spirit and the power from God must be understood as nothing other than the Word, who is also the firstborn of God, as the prophet Moses foretold; this Word, coming upon the virgin and overshadowing her, made her pregnant not by sexual intercourse but by divine power. The name Jesus, in the Hebrew tongue, means Savior in the Greek language; therefore the angel also said to the virgin, 'You shall call his name Jesus, for he will save his people from their sins.' Since the prophets prophesy by no other deity than the divine Word, I expect that you yourselves will acknowledge this as well.
Greek
Καὶ πάλιν ὡς αὐτολεξεὶ διὰ παρθένου μὲν τεχθησόμενος διὰ τοῦ Ἡσαΐου προεφητεύθη, ἀκούσατε. Ἐλέχθη δὲ οὕτως· „Ἰδοὺ ἡ παρθένος ἐν γαστρὶ ἕξει καὶ τέξεται υἱόν, καὶ ἐροῦσιν ἐπὶ τᾷ ὀνόματι αὐτοῦ Μεθ᾿ ἡμῶν ὁ θεός“. Ἃ γὰρ ἦν ἄπιστα καὶ ἀδύνατα νομιζόμενα παρὰ τοῖς ἀνθρώποις γενήσεσθαι, ταῦτα ὁ θεὸς προεμήνυσε διὰ τοῦ προφητικοῦ πνεύματος μέλλειν γίνεσθαι, ἵνα ὅταν γένηται μὴ ἀπιστηθῇ, ἀλλ᾿ ἐκ τοῦ προειρῆσθαι πιστευθῇ. Ὅπως δὲ μή τινες, μὴ νοήσαντες τὴν δεδηλωμένην προφητείαν, ἐγκαλέσωσιν ἡμῖν ἅπερ ἐνεκαλέσαμεν τοῖς ποιηταῖς, εἰποῦσιν ἀφροδισίων χάριν ἐληλυθέναι ἐπὶ γυναῖκας τὸν Δία, διασαφῆσαι τοὺς λόγους πειρασόμεθα. Τὸ οὖν „Ἰδοὺ ἡ παρθένος ἐν γαστρὶ ἕξει“ σημαίνει οὐ συνουσιασθεῖσαν τὴν παρθένον συλλαβεῖν· εἰ γὰρ ἐσυνουσιάσθη ὑπὸ ὁτουοῦν, οὐκ ἔτι ἦν παρθένος· ἀλλὰ δύναμις θεοῦ ἐπελθοῦσα τῇ παρθένῳ ἐπεσκίασεν αὐτήν, καὶ κυοφορῆσαι παρθένον οὖσαν πεποίηκε. Καὶ ὁ ἀποσταλεὶς δὲ πρὸς αὐτὴν τὴν παρθένον κατ᾿ ἐκεῖνο τοῦ καιροῦ ἄγγελος θεοῦ εὐηγγελίσατο αὐτὴν εἰπών· „Ἰδοὺ συλλήψῃ ἐν γαστρὶ ἐκ πνεύματος ἁγίου καὶ τέξῃ υἱόν, καὶ υἱὸς ὑψίστου κληθήσεται, καὶ καλέσεις τὸ ὄνομα αὐτοῦ Ἰησοῦν, αὐτὸς γὰρ σώσει τὸν λαὸν αὐτοῦ ἀπὸ τῶν ἁμαρτιῶν αὐτῶν“, ὡς οἱ ἀπομνημονεύσαντες πάντα τὰ περὶ τοῦ σωτῆρος ἡμῶν Ἰησοῦ Χριστοῦ ἐδίδαξαν, οἷς ἐπιστεύσαμεν, ἐπειδὴ καὶ διὰ Ἡσαΐου τοῦ προδεδηλωμένου τὸ προφητικὸν πνεῦμα τοῦτον γεννησόμενον, ὡς προεμηνύομεν, ἔφη. Τὸ πνεῦμα οὖν καὶ. τὴν δύναμιν τὴν παρὰ τοῦ θεοῦ οὐδὲν ἄλλο νοῆσαι θέμις ἢ τὸν λόγον, ὃς καὶ πρωτότοκος τῷ θεῷ ἐστι, Μωϋσῆς ὁ προδεδηλωμένος προφήτης ἐμήνυσε· καὶ τοῦτο ἐλθὸν ἐπὶ τὴν παρθένον καὶ ἐπισκιάσαν οὐ διὰ συνουσίας ἀλλὰ διὰ δυνάμεως ἐγκύμονα κατέστησε. Τὸ δὲ Ἰησοῦς, ὄνομα τῇ ἑβραΐδι φωνῇ, σωτὴρ τῇ ἑλληνίδι διαλέκτῳ δηλοῖ. Ὅθεν καὶ ὁ ἄγγελος πρὸς τὴν παρθένον εἶπε· „Καὶ καλέσεις τὸ ὄνομα αὐτοῦ Ἰησοῦν· αὐτὸς γὰρ σώσει τὸν λαὸν αὐτοῦ ἀπὸ τῶν ἁμαρτιῶν αὐτῶν“. Ὅτι δὲ οὐδενὶ ἄλλῳ θεοφοροῦνται οἱ προφητεύοντες εἰ μὴ λόγῳ θείῳ, καὶ ὑμεῖς, ὡς ὑπολαμβάνω, φήσετε.