There [in John 6:68–69] speaks Peter, upon whom the Church would be built, teaching in the name of the Church and showing that even if a stubborn and proud multitude withdraws because it does not wish to obey, the Church does not withdraw from Christ. The people joined to the priest, and the flock clinging to their shepherd in the Church. You ought to know, then, that the bishop is in the Church and the Church in the bishops; and if someone is not with the bishop, he is not in the Church. They vainly flatter themselves who creep up, not having peace with the priest of God, believing that they are secretly in communion with certain individuals. For the Church, which is one and catholic, is not split or divided, but is indeed united and joined by the cement of priests who adhere to one another.

St Cyprian of Carthage, Epistles, 66:8