There are those today who claim that the Bible teaches that there are Christians who are not members of the church of Christ. But I have no hesitation in affirming that the Bible teaches that every person who is a Christian is, a member of the church of Christ. This means, obviously, that I am affirming that the Bible teaches that there are no Christians who are not members of the church of Christ. The church of Christ is the body of Christ (Ephesians 1:22-23; Colossians 1: 18). The saved are those who have been reconciled unto God, and those who have been reconciled unto God are members of the body (church) of Christ (Ephesians 2:13-18). The matter is really just that simple, but in the light of the importance of the matter, let us say a bit more about it.
The Bible teaches that salvation is in Christ (II Timothy 2:10). To be in Christ is to be in His church (Galatians 3:26-27; I Corinthians 12:13; Mark 16:15-16; Acts 20:28; Acts 2:38; Ephesians 1:7; et al.). The Bible teaches that it is impossible for one to “cross the line” into salvation without “crossing the line” into Christ. The Bible also teaches that it is impossible for one to “cross the line” into Christ without “crossing the line” into the church.
The crucial relation of the church to salvation is seen in the statement, “And the Lord added (Greek imperfect “was adding,” TBW) to the church daily such as should be saved” (Acts 2:47, KJV). The English Revised Version, in an excellent treatment, translates Acts 2:47 in this way: “And the Lord added to them day by day those that were being saved” (Greek present participle).
In short, the Bible teaches that there are no Christians outside of the church for which Jesus died. When one obeys the Gospel, being baptized (as a penitent believer) in the name of Christ (that is, by His authority), the Lord adds him to the church. He never fails to do this (cf. Acts 2:41, 47; I Corinthians 12:13).
Thomas B. Warren
The Spiritual Sword (April 1985), p. 6