Sermo prosphoneticus ad Alexandrinos de fide

From the holy Cyril, from the prosphonetic discourse to the Alexandrians concerning faith. I do not accept the mixture; for it is foreign to the apostolic faith and to the correct tradition of God. For the blending works a disappearance of the natures. But the ineffable union, confessed by those who think rightly, preserves both natures unconfused, and produces one Christ, who is seen from both, the same being both God and man, and not two Christs, but one only, united and not mixed. For if the two natures, being of different substances, are blended into one mixture, neither is preserved, but both, being confounded, are annihilated. And when mixed, they admit neither separation from each other nor division; but they were divided at the time of death and separated, the soul with the divinity descending into Hades, and the body from the soul being placed in a new tomb, according to the truthful words of Christ saying, "Destroy this temple, and in three days I will raise it." And the temple is destroyed at the time of the three-day burial, by his will, and he raised it again, and was united to it by some ineffable and unspeakable principle, not mixed in it, nor incarnated, but preserving in himself the unconfused property of the two natures of different substances; for the natures were not blended.

Then he adduces a testimony from the holy Athanasius himself, as follows: "Of two natures of different substance in one Christ, the Son of God, being preserved, and neither confused, nor destroyed, nor divided." For he was made like us in all things without sin; not that the divine nature was changed or blended with the human nature, but that it was united to it not by change, not by mixture, not by mingling, not by confusion, not by alteration, not by transformation, not by annihilation or desarcification, but by a union ineffable, indescribable, and inexpressible, the two natures of different substance in one Jesus Christ, who is the Son of God, being preserved and neither confused nor destroyed nor divided. From Cyril, from the discourse on faith. But he constructed for himself a living and perfect temple in the holy virginal womb; and having put it on and been united with it by an ineffable word, both natures being preserved and not blended, he came forth, appearing as a man, but understood as God, Jesus Christ.