The Christians of the first century came into Christ’s body as they obeyed the gospel. When they “obeyed from the heart that form of doctrine,” they then became “the servants of righteousness.” (Romans 6:17,18.) Salvation was not (and is not) earned or merited, yet it has always followed obedience to the simple gospel. The vengeance of Christ awaits all those who “obey not the gospel of our Lord Jesus Christ.” (2 Thessalonians 1:7-9.) Those honest souls in the New Testament times understood that to be a Christian, one must obey the gospel and the gospel alone.
An honest, searching heart can take the New Testament and nothing else, read, believe and obey it and become a Christian, a member of the church of Christ. No denomination under heaven can claim the same for itself. To become a member of a denomination, one requires the Bible plus something else. The sectarian spirit of denominationalism would encourage the study of party platforms over the individual study of scripture. The church has nothing to fear from her members studying the Bible. The Bible, and the Bible only, has always been the seed by which children of God have been begotten.
We must never make or devise a creed, written or unwritten, to stand in competition with the inspired scriptures. If one requires something in addition to the New Testament to become one of us, we have ceased to be the simple, New Testament church.