Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Fourth Ecumenical Council.  The Council of Chalcedon.: The Letter of Cyril to John of Antioch.

p. 251 The Letter of Cyril to John of Antioch.

(Found in Labbe and Cossart, Concilia, Tom. IV., col. 343 and col. 164; and in Migne, Pat. Græc., Tom. LXXVII.  [Cyrilli Opera, Tom. X.], col. 173.  This is the letter which is often styled “the Ephesine Creed.”)

Cyril to my lord, beloved brother, and fellow minister John, greeting in the Lord.

“Let the heavens rejoice, and let the earth be glad” for the middle wall of partition has been taken away, and grief has been silenced, and all kind of difference of opinion has been removed; Christ the Saviour of us all having awarded peace to his churches, through our being called to this by our most devout and beloved of God kings, who are the best imitators of the piety of their ancestors in keeping the right faith in their souls firm and immovable, for they chiefly give their mind to the affairs of the holy Churches, in order that they may have the noted glory forever and show forth their most renowned kingdom, to whom also Christ himself the Lord of powers distributes good things with plenteous hand and gives to prevail over their enemies and grants them victory.  For he does not lie in saying:  “As I live saith the Lord, them that honour me, I will honour.”  For when my lord, my most-beloved-of-God, fellow-minister and brother Paul, had arrived in Alexandria, we were filled with gladness, and most naturally at the coming of such a man as a mediator, who was ready to work beyond measure that he might overcome the envy of the devil and heal our divisions, and who by removing the offences scattered between us, would crown your Church and ours with harmony and peace.

Of the reason of the disagreement it is superfluous to speak.  I deem it more useful both to think and speak of things suitable to the time of peace.  We were therefore delighted at meeting with that distinguished and most pious man, who expected perhaps to have no small struggle, persuading us that it is necessary to form an alliance for the peace of the Church, and to drive away the laughter of the heterodox, and for this end to blunt the goads of the stubbornness of the devil.  He found us ready for this, so as absolutely to need no labour to be bestowed upon us.  For we remembered the Saviour’s saying; “My peace I give unto you, my peace I leave with you.”  We have been taught also to say in prayers:  “O Lord our God give us peace, for thou hast given us all things.”  So that if anyone should be in the participation of the peace furnished from God, he is not lacking in any good.  That as a matter of fact, the disagreement of the Churches happened altogether unnecessarily and inopportunely, we now have been fully satisfied by the document brought by my lord, the most pious bishop Paul, which contains an unimpeachable confession of faith, and this he asserted to have been prepared, by your holiness and by the God-beloved Bishops there.  The document is as follows, and is set down verbatim in this our epistle.

Concerning the Virgin Mother of God, we thus think and speak; and of the manner of the Incarnation of the Only Begotten Son of God, necessarily, not by way of addition but for the sake of certainty, as we have received from the beginning from the divine Scriptures and from the tradition of the holy fathers, we will speak briefly, adding nothing whatever to the Faith set forth by the holy Fathers in Nice.  For, as we said before, it suffices for all knowledge of piety and the refutation of all false doctrine of heretics.  But we speak, not presuming on the impossible; but with the confession of our own weakness, excluding those who wish us to cling to those things which transcend human consideration.

We confess, therefore, our Lord Jesus Christ, the Only Begotten Son of God, perfect God, and perfect Man of a reasonable soul and flesh consisting; begotten before the ages of the Father according to his Divinity, and in the last days, for us and for our salvation, of Mary the Virgin according to his humanity, of the same substance with his Father according to his Divinity, and of the same substance with us according to his humanity; for there became a union of two natures.  Wherefore we confess one Christ, one Son, one Lord.

According to this understanding of this p. 252 unmixed union, we confess the holy Virgin to be Mother of God; because God the Word was incarnate and became Man, and from this conception he united the temple taken from her with himself.

For we know the theologians make some things of the Evangelical and Apostolic teaching about the Lord common as pertaining to the one person, and other things they divide as to the two natures, and attribute the worthy ones to God on account of the Divinity of Christ, and the lowly ones on account of his humanity [to his humanity].

These being your holy voices, and finding ourselves thinking the same with them (“One Lord, One Faith, One Baptism,”) we glorified God the Saviour of all, congratulating one another that our churches and yours have the Faith which agrees with the God-inspired Scriptures and the traditions of our holy Fathers.

Since I learned that certain of those accustomed to find fault were humming around like vicious wasps, and vomiting out wretched words against me, as that I say the holy Body of Christ was brought from heaven, and not of the holy Virgin, I thought it necessary to say a few words concerning this to them:

O fools, and only knowing how to misrepresent, how have ye been led to such a judgment, how have ye fallen into so foolish a sickness?  For it is necessary, it is undoubtedly necessary, to understand that almost all the opposition to us concerning the faith, arose from our affirming that the holy Virgin is Mother of God.  But if from heaven and not from her the holy Body of the Saviour of all was born, how then is she understood to be Mother of God?  What then did she bring forth except it be true that she brought forth the Emmanuel according to the flesh?  They are to be laughed at who babble such things about me.  For the blessed prophet Isaiah does not lie in saying “Behold the Virgin shall conceive and bear a Son, and shall call his name Emmanuel, which being interpreted is God with us.”  Truly also the holy Gabriel said to the Blessed Virgin:  “Fear not, Mary, for thou hast found favour with God.  And, behold, thou shalt conceive in thy womb, and bring forth a Son, and shall call his name Jesus.  He shall save his people from their sins.”

For when we say our Lord Jesus Christ descended from heaven, and from above, we do not so say this as if from above and from heaven was his Holy Flesh taken, but rather by way of following the divine Paul, who distinctly declares:  “the first man is of the earth, earthy; the Second Man is the Lord from heaven.”

We remember too, the Saviour himself saying, “And no man hath ascended up to heaven, but he that came down from heaven, even the Son of Man.”  Although he was born according to his flesh, as just said, of the holy Virgin, yet God the Word came down from above and from heaven.  He “made himself of no reputation, and took upon him the form of a servant,” and was called the Son of Man, yet remaining what he was, that is to say God.  For he is unchanging and unchangeable according to nature; considered already as one with his own Flesh, he is said to have come down from heaven.

He is also called the Man from heaven, being perfect in his Divinity and perfect in his Humanity, and considered as in one Person.  For one is the Lord Jesus Christ, although the difference of his natures is not unknown, from which we say the ineffable union was made.

Will your holiness vouchsafe to silence those who say that a crasis, or mingling or mixture took place between the Word of God and flesh.  For it is likely that certain also gossip about me as having thought or said such things.

But I am far from any such thought as that, and I also consider them wholly to rave who think a shadow of change could occur concerning the Nature of the Word of God.  For he remains that which he always was, and has not been changed, nor can he ever be changed, nor is he capable of change.  For we all confess in addition to this, that the Word of God is impassible, even though when he dispenses most wisely this mystery, he appears to ascribe to himself the sufferings endured in his own flesh.  To the same purpose the all-wise Peter also said when he wrote of Christ as having “suffered in the flesh,” and not in the nature of his ineffable godhead.  In order that he should be believed to be the Saviour of all, by an economic appropriation to himself, as just said, he assumed the sufferings of his own Flesh.

p. 253 Like to this is the prophecy through the voice of the prophet, as from him, “I gave my back to the smiters, and my cheeks to them that plucked off the hair:  I hid not my face from shame and spitting.”  Let your holiness be convinced nor let anyone else be doubtful that we altogether follow the teachings of the holy fathers, especially of our blessed and celebrated Father Athanasius, deprecating the least departure from it.

I might have added many quotations from them also establishing my words, but that it would have added to the length of my letter and it might become wearisome.  And we will allow the defined Faith, the symbol of the Faith set forth by our holy Fathers who assembled some time ago at Nice, to be shaken by no one.  Nor would we permit ourselves or others, to alter a single word of those set forth, or to add one syllable, remembering the saying:  “Remove not the ancient landmark which thy fathers have set,” for it was not they who spoke but the Spirit himself of God and the Father, who proceedeth also from him, and is not alien from the Son, according to his essence.  And this the words of the holy initiators into mysteries confirm to us.  For in the Acts of the Apostles it is written:  “And after they were come to Mysia, they assayed to go into Bithynia; but the Spirit of Jesus suffered them not.”  And the divine Paul wrote:  “So then they that are in the flesh cannot please God.  But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you.  Now if any man have not the Spirit of Christ, he is none of his.”

When some of those who are accustomed to turn from the right, twist my speech to their views, I pray your holiness not to wonder; but be well assured that the followers of every heresy gather the occasions of their error from the God-inspired Scriptures, corrupting in their evil minds the things rightly said through the Holy Spirit, and drawing down upon their own heads the unquenchable flame.

Since we have learned that certain, after having corrupted it, have set forth the orthodox epistle of our most distinguished Father Athanasius to the Blessed Epictetus, so as thereby to injure many; therefore it appeared to the brethren to be useful and necessary that we should send to your holiness a copy of it from some correct ancient transcripts which exist among us.  Farewell.