On the day of Pentecost, when the church was birthed, the apostle Peter stood up boldly and authoritatively and preached the Word and pointed people to Christ as Lord God and Savior. The Spirit of God pierced the hearts of the people, convicting them of their sin, and they cried out wanting to know how they should respond. The best response to the Word of God rightly handled is to ask what you should do!

They were told to repent, which implies belief, and then be baptized because of the forgiveness of their sins. That day about 3000 people believed and were baptized and were added to the church. The adding in of new believers is the first instance of church membership. Jesus had already said in Matthew 28:18–20 his followers were to go into all the world and preach the gospel, making disciples of all nations, baptizing them in the name of the Father and the Son and the Holy Spirit, and teaching them to observe all that Jesus commanded. The teaching is done after people come to faith in Christ, and are baptized in obedience to Jesus. And that teaching is to be done in the fellowship of a local church.

In 1 Corinthians 12 it speaks a lot about members of the body, the Greek word is melos, which means body parts. The same word is also used a lot in Ephesians, and the metaphor of members of an actual body makes a lot of sense. And when that word is used, it's always in context of a local church assembly.

In the New Testament, believer’s baptism by immersion in water was the church accepting and confirming a person’s testimony, and accepting them into fellowship with a local assembly. They become a part of a local body of believers.

There’s no formal process outlined, it just happened because it was commanded (Matt. 28:18-20). It was a natural outflow of Christ saving a person. You believe, you are baptized in obedience to Jesus, and you come into the church under the care of a united group of elders. As noted in our Grace Church of Orange membership paper (https://www.csmedia1.com/graceorange.org/gco-position-paper-on-church-membership-1.pdf) there are ample reasons, some implicit, some explicit, which illustrate the same truths.

That said, it is preferable if you get baptized soon after coming to faith in Christ/conversion, and join the church upon your testimony of faith. These two obedient acts should preferably not be separated by time, but done somewhat concurrently, in order to get a person on a path of spiritual growth right away after coming to faith in Christ.

The reason why this is so important, why baptism and church membership should be more of a unified process, is because the elders of a local assembly are charged by God to keep watch over the souls of the believers in that assembly. All for their growth and for vibrant Christian witness.

The New Testament knows no example of someone just getting baptized by a church and not uniting with that church in worship and witness. The only possible example would be the unique example of Philip, and the Ethiopian eunuch in Acts chapter 8. But if we’re understanding the story correctly, the Spirit of God had that happen, and then snatched Philip away, and sent the eunuch on his way, presumably to go home and start a church where he lived. A baptized believer going back to Africa. First time it ever happened.

So let's pattern our baptisms and church membership as closely to the scriptural pattern as we can. Let's link baptism and church membership more closely. Let's see them as part of a unified process to glorify God, build up believers, and reach the world.