The true Church is the one that continues in the traditions, teachings and practices of the New Testament Church. Our Bible study aid booklet The Church Jesus Built details the transformation and corruption by reformers of many teachings given by Jesus Christ to His disciples. God's Church rejects the doctrines men have added or changed, and it holds to "the faith which was once for all delivered" (Jude 3).
An important tenet of Jesus' teachings was the gospel of the Kingdom of God. The role and work of the Son of God is central to the gospel. However, most churches preach only a message about the person of Christ, saying much about His role as Savior but little about His role as King. In other words, most churches do not preach the gospel that Jesus did. Jesus came as a special Messenger (Malachi 3:1) of the Kingdom of God—as well as the Savior. The true Church will also be preaching this gospel to the world as a witness (Matthew 24:14).
Another key in identifying the true Church is the correct day of worship. Jesus customarily observed the seventh day, the Sabbath (Luke 4:16), the day that God set aside at creation for worship (Exodus 20:8-11). Scripture reveals that the Sabbath is a perpetual sign or an identifying mark of the people of God (Exodus 31:12-17), meaning that the Church of God would be observing it today. Most churches say that the Sabbath law is no longer binding or that God caused Sunday worship to supersede it. They're wrong.
The Church Jesus Built discusses these topics more thoroughly. It shows the beginnings of a counterfeit Christianity in the first century. Several books of the New Testament mention false teachers infiltrating the Church with corrupting ideas. They combined bits and pieces of pagan religions with Christian concepts and convinced many to follow their ways. Satan has taken great advantage of these circumstances (2 Corinthians 11:13-14) and has created a counterfeit church to parallel the true one. Through the intervening centuries, people accepted the counterfeit over the true Church. The Bible study aid explains the doctrines and practices of the early New Testament Church of God, so those who would like to find it today can do so.