Many people have been saved and have truly come to know Christ after having been sincere, religious “church members” for years. Though faithful supporters of some earthly church organization they had never experienced the truth of II Cor. 5:17: “If any man [be] in Christ there is a new creation.” It is possible to be a member in good standing of a church organization, yet be outside the one true Church of which the Bible speaks.
This is because the true Bible Church is not an organization, much less a political state. It is a living organism, a spiritual body, with a living Head and living members. Again and again St. Paul, by divine inspiration, calls the Church, the Body of Christ (Rom. 12:5; I Cor. 12:27; Eph. 5:30).
It should be observed too, that the true Bible Church has one Head — not a man on earth, but the glorified Christ in heaven (Eph. 1:22; 4:4,5; 5:23; Col. 1:18). Nowhere in Scripture do we read that any man is to act as His earthly representative as Head of the Body.
How, then, do we become members of this one true Bible Church, the Body of Christ? First, we must acknowledge ourselves to be sinners in God’s sight, for Ephesians 2:16 relates how Christ died for sinful men “that He might RECONCILE both [Jew and Gentile] to God in one Body by the cross, having slain the enmity thereby.” Thus, when believing sinners are RECONCILED to God by faith in Christ, they are REGENERATED, given a new life, by the Spirit, and by the Spirit are BAPTIZED into the Church, the Body of Christ.
“For BY ONE SPIRIT ARE WE ALL BAPTIZED INTO ONE BODY” (I Corinthians 12:13).
Every one of us should ask himself: “Have I been baptized by the Spirit into the Body of Christ?” Those who have not, do not belong to the one Church which God recognizes. But membership in the true Church is still open. Simply, but sincerely, trust Christ as your Savior. He is the Head of the Church. “Believe on the Lord Jesus Christ and thou shalt be saved” (Acts 16:31). Then associate yourself with some local assembly where Christ is honored and the Bible taught, rightly divided. source