In Mt. 16:18, Jesus stated that He would build His church. At that point in time, the church was still in the future. The church was spoken of as being present after the baptism of about three thousand souls on the Pentecost following Jesus’ resurrection (Acts 2:47). The previous verse stated that they continued “daily with one accord…” (Acts 2:46). They were united.
The night of His arrest, Jesus had prayed for the unity of His followers; “…that they all may be one, as You, Father, are in Me, and I in You; that they may be one in Us…that they may be one just as We are one: I in them, and You in Me; that they may be made perfect in one…” (Jn. 17:20-23)
Adam and Eve were united with God in the Garden of Eden. However, Satan convinced them to eat of the forbidden fruit. That drove a wedge between God and man. Since that time, man has always had a “better idea” of how to do things his way instead of in God’s way.
Man’s tendency “to do it my way” became evident in the Corinthian church when Christians began following other men (I Cor. 1:10-13). Paul warned the Antioch elders to beware of false teachers (Acts 20:28-31). Likewise, he warned Timothy in I Tim. 4:1-3 of doctrines of demons that would deceive the church.
Even before the end of the first century, there were congregations of the Lord’s church who were allowing false teachings to defile their Christianity. See the letters to the churches of Asia in Rev. 2:1-3:22.
Before long, men began to add various changes to the church’s leadership. Eventually, they placed the pope in Rome as “head of the church on earth” and called themselves Catholics. The Catholic Church claims to be the original church of the New Testament. In a sense, they are correct, but with the many additions and changes that have been made, it has devolved to be unrecognizable as the New Testament church.