One of the tragic aberrations of so-called modern religion is "Churchless Christianity."The assertion is that it is Christ who saves us, not the Church, so "all you need is Jesus."
Few who claim to be Christians, would argue that it is Christ who saves. For He is the eternal Son of God who has assumed human flesh, and has done so "for us and for our salvation." Thus Paul writes, "for there is one God and one Mediator between God and men, the Man Christ Jesus" (1Ti 2:5). But because this Mediator established the Church which is His Body, we who are joined to Him are joined to His Church as well. To say we love Christ, who is the Head of the Church and at the same time reject His Body is to deny New Testament teaching.
The first use of the word "church" in the New Testament comes in the Gospel of Matthew, when our Lord gives His approval of Peter;s confession of faith and promises, "I will build My church" (Mt 16:18). Jesus Christ builds and we cooperate with Him.
The Book of Acts amplifies what Jesus meant in Matthew 16. When Peter;s sermon on the day of Pentecost concludes, those present ask for guidance toward salvation: "What shall we do?" (Acts 2:37). Following Peter's word, they are baptized and join with the other believers, three thousand of them (Acts 2:38, 41).
Having been joined to Christ and HIs Church, these baptized believers begin living as the body of Christ . We find them looking after each other, using their personal resources for one another's care, continuing together in prayer and in the Eucharist (Acts 2:42-47). From this point on " the Lord added to the church daily those who were being saved" (Acts 2:47), and through out Acts, we see the Church being built as the Gospel of Christ spreads.
Credits: from the Orthodox Study Bible.