Formula of union between Cyril and John of Antioch

We will state briefly what we are convinced of and profess about the God-bearing virgin and the manner of the incarnation of the only begotten Son of God -- not by way of addition but in the manner of a full statement , even as we have received and possess it from of old from the holy scriptures and from the tradition of the holy fathers, adding nothing at all to the creed put forward by the holy fathers at Nicaea. For, as we have just said, that creed is sufficient both for the knowledge of godliness and for the repudiation of all heretical false teaching. We shall speak not presuming to approach the unapproachable; but we confess our own weakness and so shut out those who would reproach us for investigating things beyond the human mind.

We confess, then, our lord Jesus Christ, the only begotten Son of God perfect God and perfect man of a rational soul and a body, begotten before all ages from the Father in his godhead, the same in the last days, for us and for our salvation, born of Mary the virgin, according to his humanity, one and the same consubstantial with the Father in godhead and consubstantial with us in humanity , for a union of two natures took place. Therefore we confess one Christ, one Son, one Lord. According to this understanding of the unconfused union, we confess the holy virgin to be the mother of God because God the Word took flesh and became man and from his very conception united to himself the temple he took from her. As to the evangelical and apostolic expressions about the Lord, we know that theologians treat some in common as of one person and distinguish others as of two natures, and interpret the god-befitting ones in connexion with the godhead of Christ and the lowly ones with his humanity.