Below is a helpful section from John Zizioulas’ book-, ‘Eucharist, Bishop, Church;” the insertion of quotations are mine.
Throughout the entire period of the first three centuries, unity was bound up at the deepest level with the faith, the prayers and the activities of the Church.
Gospel reflects this fact when it
presents the unity of the Church as an agonized petition in the prayer of the
Lord. St John's
John 17.11 and 20 f.: "Holy Father, keep them in Thy name, which Thou hast given Me, that they may be one even as We are one... I do not pray for these only, but also for those who believe in Me through their word, that they may all be one, that the world may believe that Thou hast sent Me." It is worth noting that
Gospel links the "agony" (Luke 22.4) of the prayer before the Passion
with the unity of the Church as is shown by the emphatic repetition of
"that they may be one". St John's
The Acts of the Apostles expresses the same reality when they emphatically stress unity as the element characteristic of the Church's life in her first years while the existence of a "theology of unity" at a period as early as that of St Paul's Epistles cannot be interpreted otherwise than as an indication of the importance which the Church from the beginning attached to her unity.
Acts 2.44f.: "And all who believed were together (epi to auto) and had all things in common; and they sold their possessions and goods and distributed them to all, as any had need."
During the years following apostolic times, the Church regarded her unity as a matter of constant concern and an object of vehement faith. The texts of the so-called Apostolic Fathers present the unity of the Church as an object of teaching, and something for which they struggled against every divisive force.
1 Clement: 49.5; Love joins us to God. Love covers a multitude of sins. Love endures all things, is patient in all things. There is nothing inferior in love, nothing arrogant in love. Love has no schism, doesn’t rebel. Love does all things in harmony. By love all the chosen ones of God have been made perfect. Without love, nothing is acceptable to God.
1 Clement: 46.5-7; Why are there strifes, and angers, and dissensions and schisms and war among you? Do we not have one God and one Christ? And one Spirit of grace poured out upon us? And one calling in Christ? Why do we divide and tear apart the members of Christ, and rebel against our own Body, and are coming to such a madness as to forget we are members of one another? Remember the words of the Lord Jesus.
1 Clement: 54.1-2; So, who among you is noble? Who compassionate? Who completely filled with love? Let him say, if because of me there are rebellion and strife and schisms, I will leave. I will go wherever you want, and do whatever the multitude commands. Only let the flock of Christ live in peace with the appointed elders.
Ignatius to the Philadelphians; 3.2; 6.2; For as many as are of God and of Jesus Christ are also with the bishop. And as many as shall, in the exercise of repentance, return into the unity of the Church, these, too, shall belong to God, that they may live which is in Syria, whence I am not worthy to derive my name: for I stand in need of your united prayer in God, and your love, that the Church which is in Syria may be deemed worthy of being refreshed by your Church. Knowing as I do that ye are full of all good, I have but briefly exhorted you in the love of Jesus Christ. Be mindful of me in your prayers, that I may attain to God; and of the Church which is in
, of whom
I am not worthy to be called bishop. For I stand in need of your united prayer
in God, and of your love, that the Church which is iaccording to Jesus Christ. Do not err, my brethren. If any man follows him that makes a schism in the Church, he shall not inherit the Syria . If any one walks according to a strange (heretical) opinion, he agrees not with the passion [of Christ.]. Flee therefore the wicked devices and snares of the prince of this world, lest at any time being conquered (oppressed) by his artifices, ye grow weak in your love. But be ye all joined togetherwith an undivided heart. kingdom of God
Ignatius to the Magnesians 14.1; 13.2; 1.2; Knowing as I do that ye are full of God, I have but briefly exhorted you. Be mindful of me in your prayers, that I may attain to God; and of the Church n Syria may be deemed worthy, by your good order, of being edified in Christ.
Didache 8.4; 10.5; Remember, Lord, Thy Church, to deliver it from all evil and to make it perfect in Thy love, and gather it from the four winds, sanctified for Thy kingdom which Thou have prepared for it; for Thine is the power and the glory for ever. Let grace come, and let this world pass away. Hosanna to the God (Son) of David! If any one is holy, let him come; if any one is not so, let him repent. Maranatha. Amen.
Around the end of the second century, Irenaeus attempts in a work especially devoted to the subject to show that the Church was and has been preserved as one, and that unity constitutes the necessary condition for her existence. A few generations later, St Cyprian devotes a special study to the subject of church unity, while in the various creedal documents; unity early assumes the character of an article of faith.