From Commentary on St. John’s Gospel (ca. 425)
Christ wishes the disciples to be kept in a state of like-mindedness and an identity of will, being mingled together as it were in soul and spirit and in the law of peace for one another. He wishes them to be bound together tightly in an unbreakable bond of love, that they may advance to such a degree of unity that their freely chosen association might even become an image of the natural unity that is conceived to exist between the Father and the Son.
That is to say, he wishes them to enjoy a unity that is inseparable and indestructible, which may not be enticed away into a dissimilarity of wills by anything at all that exists in the world or any pursuit of pleasure, but rather reserves the power of love in the unity of devotion and holiness. And this is what happened. For we read in the Acts of the Apostles, “the company of those who believed were of one heart and soul,” that is, in the unity of the Spirit. This is also what Paul himself meant when he said, “one body and one Spirit.” We who are many are one body in Christ, for we all partake of the one bread,” and we have all been anointed in the one Spirit, the Spirit of Christ.
St. Cyril of Alexandria (376-444) was Patriarch of Alexandria and an influential theologian, who convened the Ecumenical Council of Ephesus in 431, which resolved the Nestorian Controversy by asserting the unity of Christ’s person, and defending the use of the Marian title “Theotokos,” the God-bearer. His commentary on St. John’s Gospel was a product of the early days of his episcopate. He is commemorated on various days on the liturgical calendar of Eastern and Western churches. This translation is taken from Norman Russell, ed., Cyril of Alexandria (London: Routledge, 2000).