From his letter to Eupsychius:-
"How then did it behave the Most Wise to act? By mediation of the flesh assumed, and by union of God the Word with man born of Mary, He is made of either nature, so that the Christ made one of both, as constituted in Godhead, abides in the proper dignity of His impassible nature, but in flesh. being brought near to death, at one and the same time shews the kindred nature of the flesh how through death to despise death, and by His death confirms the righteousness of the new covenant."
Testimony of Cyril, bishop of Alexandria.
From his letter to Nestorius: -
"The natures which have been brought together in the true unity are distinct, and of both there is one God and Son, but the difference of the natures has not been removed in consequence of the union."
Of the same from his letter against the Orientals: -
"There is an union of two natures, wherefore we acknowledge one Christ, one Son, one Lord. In accordance with this perception of the unconfounded union we acknowledge the Holy Virgin as Mother of God because the Word of God was made flesh and was made man, and from the very conception united to Himself the temper taken from her."
Of the same:-
"There is one Lord Jesus Christ, even if the difference be recognised of the natures of which we assert the ineffable union to have been made."
Of the same:-
"Therefore, as I said, while praising the manner of the incarnation, we see that two natures came together in inseparable union without confusion and without division, for the flesh is flesh and no kind of Godhead, although it was made flesh of God; in like manner the Word is God, and not flesh, although He made the flesh His own according to the oeconomy."
Of the same from his interpretation of the Epistle to the Hebrews:-
"For although the natures which came together in unity are regarded as different and unequal with one another, I mean of flesh and of God, nevertheless the Son, Who was made of both, is one."
Of the same from his interpretation of the same Epistle:-
"Yet though the only begotten Word of God is said to be united in hypostasis to flesh, we deny there was any confusion of the natures with one another, and declare each to remain what it is."
Of the same from his commentaries:-
"The Father's Word, born of the Virgin, is named man, though being by nature God as partaking of flesh and blood like us for thus He was seen by men upon earth, without getting rid of His own nature, but assuming our Manhood perfect according to its own reason."
Of the same concerning the Incarnation (Schol. c. 13):-
"Then before the incarnation there is one Very God, and in manhood He remains what He was and is and will be; the one Lord Jesus Christ then must not be separated into man apart and into God apart, but recognising the difference of the natures and preserving them unconfounded with one another, we assert that there is one and the same Christ Jesus."
Of the same after other commentaries:-
"There is plain perception of one thing dwelling in another, namely the divine nature in manhood, without undergoing commixture or any confusion, or any change into what it was not. For what is said to dwell in another does not become the same as that in which it dwells, but is rather regarded as one thing in another. But in the nature of the Word and of the manhood the difference points out to us a difference of natures alone, for of both is perceived one Christ. Therefore he says that the Word `Tabernacled among us,' carefully observing the freedom from confusion, for he recognises one only begotten Son who was made flesh and became man."
Now, my dear sir, you have heard the great lights of the world; you have seen the beams of their teaching, and you have received exact instruction how, not only after the nativity, but after the passion which wrought salvation, and the resurrection, and the ascension, they have shewn the union of the Godhead and of the manhood to be without confusion.
Eran. -I did not suppose that they distinguished the natures after the union, but Ihave found an infinite amount of distinction.
Orth. -It is mad and rash against those noble champions of the faith so much as to wag your tongue. But I will adduce for you the words of Apollinarius, in order that you may know that he too asserts the union to be without confusion. Now hear his words.
Testimony of Apollinarius.