The command of the Scriptures is that one must be born of water and the Spirit to enter the kingdom of God. Being born by Christian parents does not make one Christian. A Christian is born of God. It is the second birth. It breaks my heart to see people especially my brethren in the flesh who believe they are Christian but are not. Such people are in all the mainstream churches. They follow the doctrine of their denominational churches rather than the unambiguous word of God in the Bible.
A born again Christian is a new creation. Unlike Jews and Gentiles, Christians are not earthly people; they are heavenly, peculiarly different from others but in the world as pilgrims and strangers.
It is the responsibility of every General Overseer, General Superintendent, supervisor, senior pastor or head of the assembly to determine the spiritual status of congregants. To assemble believers and unbelievers in the same service is a disservice to the body of Christ. In the early church it was not so. “Now all who believed were together, and had all things in common … continuing daily with one accord in the temple, and breaking bread from house to house” (Acts 2:44-46).
Separate the sheep from the goats. Preach the gospel of grace of God to unbelievers. Teach, exhort and grow believers with the doctrines of Christ. Separate marriages joined by God from mixed and ungodly unions and deal with the latter to save the souls of those concerned who may not know they are in danger of missing heaven.
An excerpt from: CHRISTIAN WEDDING: What the Bible Teaches.