What is Christianity? Is it a religion just like any other religion? Religion is man’s work to reach God. Christianity is not men’s work, but God’s work. It is God’s work to reach men. What God wants from men is a relationship with Him through the Lord Jesus Christ. That is true Christianity.
Everyone who is truly born again (a true believer) is justified by the blood of the Lord Jesus Christ in the sight of God. He is saved from the punishment of sin. Besides, he is also sanctified by the Holy Spirit so that he can live a righteous and holy life. He is saved from the power of sin. Having been born again, this believer is called into the fellowship (relationship) of God’s Son, the Lord Jesus Christ (1 Cor 1:9). What is the purpose of this fellowship? To keep his sanctified life, to keep him from falling into sin. Even, if he falls into sin, he will be able to immediately repent from his sin.
However, if a believer continues to live in sin, he will lose his zeal for God. When he loses his zeal, he will stop having a relationship with God. He will still probably go to church, and even serve in the church, but he has moved into works; having a form of godliness but denying its power(2 Tim 3:5). What he has is no longer a relationship, but a religion.
To prevent a believer from moving into religion because of his continual sinning, first, he must know and believe that Jesus Christ died on the cross not only to save him from the punishment of sin but to set him free from the power of sin as well. The grace of the cross is the deliverance from sin as well as the forgiveness of sin. Second, he must understand that being a Christian does not mean that he cannot sin. He still can sin if he chooses to. Therefore, he must choose not to sin to experience the grace of deliverance from sin.