In the second chapter of Acts, we read that in Jerusalem on the day Jewish feast day of Pentecost following the resurrection and ascension of Christ, the apostle Peter preached the gospel of Christ.  Thousands were present that day to hear him speak.

     They believed the message and when they asked, "What must we do?", Peter announced the conditions of salvation (forgiveness of sins).  He said, "Repent and be baptized every one of you in the name of Jesus Christ for the remission of sins" (Acts 2:38). Three thousand souls gladly heard the word and were baptized (Acts 2:41).  Upon their faith in and obedience to Christ they were saved and added to his church (Acts 2:47). Jesus had said he would "build my church" (Matthew 16:18) and here in Acts chapter two we find him doing just that through the preaching of the gospel message.

     Although these three thousand souls believed and obeyed the gospel, received the forgiveness of sins, and were added to the church, they did not join any denomination or religious sect.  They were just Christians, Christians only, members of Christ's church.  This, only this, and nothing more.