Christ is One

And this I say having read Nestorius’ words and observing that he not only says that we ought not to say that the holy Virgin is Mother of God and that she hath borne Emmanuel Who is God, but yet in addition to this and in many ways is he minded to make war upon the glory of Christ. For he endeavours to shew us that He is God-bearing and not truly God, but man associated with God, as in equality of rank. For thus seems good to him alone apart from every one else, to think and to speak, albeit the Catholic Church, which Christ Himself presented to Himself, has not the wrinkles of him who has compiled such things, but rather as unblemished, she keeps wholly without rebuke her knowledge of Him, and hath made full well her tradition of the Faith. For we believe in One God, the Father Almighty, of all things both visible and invisible the Maker, and in One Lord Jesus the Christ, and in the Holy Ghost: and following the confessions annexed hereto of the holy Fathers, we say that the Very Word Essentially sprung from forth God the Father, was made as we and was Incarnate and made Man, that is, took to Himself a Body from forth the holy Virgin, and made it His Own: for thus will He be truly One Lord Jesus Christ, thus let us worship Him as One, not putting apart Man and God, but believing that He is One and the Same, in Godhead and in Manhood, that is, God alike and Man.

Cyril of Alexandria – Five Tomes against Nestorius; Scholia on the Incarnation; Christ Is One; Fragments against Diodore of Tarsus, Theodore of Mopsuestia, the Synousiasts (39). London; Oxford; Cambridge: James Parker and Co.; Rivingtons.