Preface
First of all, it is important to note that in the Bible there is not a single example and not a single basis for creating one’s own churches and proclaiming oneself their pastor. Christ created one visible Church and expressed His will for its unity.
The Will of Christ and the Apostles for the Visible Unity of the Church
“I do not pray for these alone, but also for those who will believe in Me through their word; that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me” (John. 17:20-21)
“Now I plead with you, brethren, by the name of our Lord Jesus Christ, that you all speak the same thing, and that there be no divisions among you, but that you be perfectly joined together in the same mind and in the same judgment. For it has been declared to me concerning you, my brethren, by those of Chloe’s household, that there are contentions among you. Now I say this, that each of you says, ‘I am of Paul,’ or ‘I am of Apollos,’ or ‘I am of Cephas,’ or ‘I am of Christ.’ Is Christ divided? Was Paul crucified for you? Or were you baptized in the name of Paul?” (1 Cor. 1:10-13) “For when one says, ‘I am of Paul,’ and another, ‘I am of Apollos,’ are you not carnal?” (1 Cor. 3:4)
God arranged the members of the body (the Church) so that there would be no divisions, but that all would care for one another, suffer together and rejoice together:
“For by one Spirit we were all baptized into one body — whether Jews or Greeks, whether slaves or free — and have all been made to drink into one Spirit. For in fact the body is not one member but many. <...> And the eye cannot say to the hand, ‘I have no need of you’; nor again the head to the feet, ‘I have no need of you’. No, much rather, those members of the body which seem to be weaker are necessary. And those members of the body which we think to be less honorable, on these we bestow greater honor; and our unpresentable parts have greater modesty, but our presentable parts have no need. But God composed the body, having given greater honor to that part which lacks it, that there should be no schism in the body, but that the members should have the same care for one another. And if one member suffers, all the members suffer with it; or if one member is honored, all the members rejoice with it” (1 Cor. 12:13-14,21-26)
What are these different members of the body? The different ministries and gifts in the Church:
“For as the body is one and has many members, but all the members of that one body, being many, are one body, so also is Christ. <...> For in fact the body is not one member but many. <...> Now you are the body of Christ, and members individually. And God has appointed these in the church: first apostles, second prophets, third teachers, after that miracles, then gifts of healings, helps, administrations, varieties of tongues. Are all apostles? Are all prophets? Are all teachers? Are all workers of miracles? Do all have gifts of healings? Do all speak with tongues? Do all interpret?” (1 Cor. 12:12,14,27-30)
Thus God arranged all these ministries and gifts so that there would be no divisions in the body, which the apostle prevents at the beginning of the epistle (1 Cor. 1:10-13). That is, God not only wants unity (John. 17:20-21), but also takes care of it. Here the apostle, appointed to the ministry by God, takes care of visible unity and forbids the Corinthians to create visible divisions.
Since unity is the will of Christ, it is important to understand that the one who will be saved is the one who does the will of God (Matt. 7:21).
Antichrists Violate the Will of Christ and Openly Go Out of the Boundaries of the Church
Antichrists go out of the apostolic communities:
“Little children, it is the last hour; and as you have heard that the Antichrist is coming, even now many antichrists have come, by which we know that it is the last hour. They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us” (1 John. 2:18-19)
They serve not Christ:
“Now I urge you, brethren, note those who cause divisions and offenses, contrary to the doctrine which you learned, and avoid them. For those who are such do not serve our Lord Jesus Christ, but their own belly, and by smooth words and flattering speech deceive the hearts of the simple” (Rom. 16:17-18)
The Original Visible Unity of the Church
Outsiders Are Separate
From the very beginning the Church had quite definite visible boundaries:
“Yet none of the rest dared join them, but the people esteemed them highly” (Act. 5:13)
Common Goods
The Church was a monolithic society:
“Now the multitude of those who believed were of one heart and one soul; neither did anyone say that any of the things he possessed was his own, but they had all things in common” (Act. 4:32)
Common Resolution of Disputed Questions
The Church has common problems and resolves them together, gathering at quite definite, visible councils:
“Now the apostles and elders came together to consider this matter. <...> Then it pleased the apostles and elders, with the whole church, to send chosen men of their own company to Antioch with Paul and Barnabas, namely, Judas who was also named Barsabas, and Silas, leading men among the brethren” (Act. 15:6,22)
Common Rules
The Church has definite rules, common to all:
“And as they went through the cities, they delivered to them the decrees to keep, which were determined by the apostles and elders at Jerusalem. So the churches were strengthened in the faith, and increased in number daily” (Act. 16:4-5)
Prohibition of Dividing into Parties
In the Church any attempts to divide are stopped:
“Now I plead with you, brethren, by the name of our Lord Jesus Christ, that you all speak the same thing, and that there be no divisions among you, but that you be perfectly joined together in the same mind and in the same judgment. For it has been declared to me concerning you, my brethren, by those of Chloe’s household, that there are contentions among you. Now I say this, that each of you says, ‘I am of Paul,’ or ‘I am of Apollos,’ or ‘I am of Cephas,’ or ‘I am of Christ.’ Is Christ divided? Was Paul crucified for you? Or were you baptized in the name of Paul?” (1 Cor. 1:10-13) “For when one says, ‘I am of Paul,’ and another, ‘I am of Apollos,’ are you not carnal?” (1 Cor. 3:4)
One Faith and the Sacraments
In the Church there is exactly one definite faith, common to all:
“one Lord, one faith, one baptism” (Eph. 4:5)
“Whoever transgresses and does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son” (2 John. 1:9)
As the Savior says, the faith is according to the word of the apostles:
“I do not pray for these alone, but also for those who will believe in Me through their word” (John. 17:20)
The Church knew that in the future there would appear people who would want to separate from the one faith. These people are not called the Church:
“how they [the apostles] told you that there would be mockers in the last time who would walk according to their own ungodly lusts. These are sensual persons, who cause divisions (Greek: ἀποδιορίζοντες — “those who separate”, i.e. who separate themselves from the unity of the faith), not having the Spirit” (Jude. 1:18-19)
One Priestly Hierarchy
“he sent to Ephesus and called for the elders of the church. And when they had come to him, he said to them: <...> take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers (Greek: ἐπισκόπους — “bishops”), to shepherd the church of God which He purchased with His own blood” (Act. 20:17-18,28)
More about the priesthood.
Thus the Church is a quite definite visible society (organism), with exactly one common apostolic faith, with rules common to all, under leaders appointed by the apostles who are united in everything, and whose members have no barriers between them.
The Boundaries of the Church and the Eucharist
The Old Testament church was not called the Body of Christ, unlike the New Testament one. The New Testament Church is a mystical divine-human organism, the Body of Christ. Therefore the boundaries of the Church are where the boundaries of the body are. Where are the boundaries of the human body? Where the blood circulates, there is the body. Where it does not circulate, there is no body. Without blood there is no life in the parts of a person. A severed hand is no longer part of the body. Rather soon, without blood, it will decay, receiving no flow of blood. Where there is true communion, there is the Body, that is, the Church:
“The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ? For we, though many, are one bread and one body; for we all partake of that one bread” (1 Cor. 10:16-17)
“Now you are the body of Christ, and members individually” (1 Cor. 12:27)
“But now in Christ Jesus you who once were far off have been brought near by the blood of Christ” (Eph. 2:13)
That is why people are saved only in the Church: because Christ is the Savior of the Body, that is, the Church:
“For the husband is head of the wife, as also Christ is head of the church; and He is the Savior of the body” (Eph. 5:23)
More about the Eucharist.
Hieromartyr Ignatius, Bishop of Antioch (1st century), Epistle to the Smyrnaeans:
“Chapter 8. … Let no man do anything connected with the Church without the bishop. Let that be deemed a proper Eucharist, which is [administered] either by the bishop, or by one to whom he has entrusted it”