Letter 23: Regarding the three days and nights of the Lord's burial: the reckoning is straightforward if you understand Jewish...

On the words "Every male that opens the womb," and against the Theopaschites [those who said the divine nature itself suffered] and those who say that there is one nature in Christ. The saying in the divine Scripture, that "Every firstborn that opens the womb is holy to the Lord," was not spoken of every firstborn (let not the unlearned suppose so), but of one and that only one, who at his birth opened the womb. For mingling and intercourse open every womb; but the womb that conceived our Lord Jesus Christ He himself opened, having been conceived without seed and coming forth, and again he left it sealed; being truly made man, and being truly also God, and worshipped from both the two natures.

Εἰς τὸ, « Πᾶν ἄρσεν διανοῖγον μήτραν, » καὶ κατὰ θεοπασχητῶν, καὶ τὴν [τ. τῶν] μίαν ἐπὶ Χριστοῦ φύσιν εἶναι λεγόντων. Τὸ εἰρημένον ἐν τῇ θείᾳ Γραφῇ, ὅτι « Πᾶν πρωτότοκον διανοῖγον μήτραν, ἅγιον τῷ Κυρίῳ, » οὐ περὶ παντὸς εἴρηται πρωτοτόκου· μὴ οὕτως οἱ ἀμαθεῖς νομιζέτωσαν· ἀλλὰ περὶ ἑνὸς [ἐκείνου] καὶ μόνου, τοῦ ἐν τῷ τίκτεσθαι τὴν μήτραν ἀνοίξαντος. Πᾶσαν γὰρ μήτραν μίξις καὶ συνουσία ἀνοίγνυσι· τὴν δὲ τὸν Κύριον ἡμῶν Ἰησοῦν Χριστὸν κυήσασαν, αὐτὸς συλληφθεὶς ἀσπόρως προερχόμενος ἤνοιξε, καὶ πάλιν ἐσφραγισμένην κατέλιπεν· ἀληθῶς (23) μὲν γενόμενος ἄνθρωπος, ἀληθῶς δὲ [ὂν καὶ] Θεὸς καὶ προσκυνούμενος ἐξ ἑξ ἀμφοτέρων τῶν φύσεων.