In terms of the Bible, the church of Christ is the collective body of saved souls—souls that have been saved by Jesus Christ, in obedience to His gospel (cf. Romans 1:16). In this way the church must be properly understood as a body of people, NOT a material building or structure. Individual souls are added to this body by the Lord Himself. People cannot be “voted” into the church of Christ. The last sentence of Acts 2:47 explains, “And the Lord added to the church daily those who were being saved” (NKJV).
How is one added to the church of Christ?
As mentioned above, only the Lord can add one to the church, making him or her a member therein. The Lord does not do this arbitrarily, however. There are commands of the gospel that one must obey. When one obeys the gospel as set forth in the Bible, the Lord adds that precious soul to His church.
Hearing and believing the gospel of Christ. In commanding that His gospel be preached in all the world, Jesus declared, “He that believeth and is baptized shall be saved; but he that believeth not shall be damned” (Mark 16:15-16). The gospel is the good news surrounding the death, burial and resurrection of Jesus Christ (cf. 1 Corinthians 15:1-4). It is the revelation of God’s will for mankind today, and its fullness is recorded as the New Testament.
Repenting of one’s sins. Jesus Christ also commanded, “And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem” (Luke 24:47). Repentance is the conscious decision wherein one turns away from sinful conduct, in order to devote his or her life to God. It is commanded of all men everywhere (Acts 17:30). Truly believing the gospel of Christ should cause one to repent, turning away from his or her sins.
Confessing Christ and putting Him on in baptism. Like Timothy, one must make the “good confession” (cf. 1 Timothy 6:12-13, NKJV). This confession was also made by the Ethiopian eunuch when he said, “I believe that Jesus Christ is the Son of God” (Acts 8:37, NKJV). Only after the eunuch had made this confession did Philip baptize him into Christ (Acts 8:38; cf. Romans 6:3-4).
In the New Testament, baptism is clearly a requirement for salvation. This is seen in the fact that baptism is for the “remission,” or washing away of sins (cf. Acts 2:38; 22:16). Only “in Christ” can one have the redemption that is made possible by His blood (Colossians 1:14). Baptism serves as the “doorway” into Christ. “For as many of you as have been baptized into Christ have put on Christ,” (Galatians 3:27). For this reason, only those who are scripturally baptized are added by the Lord to His church (Acts 2:41, 47).