2 Corinthians 5:17 Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come.
We learned from John 3:3 that regeneration is required for a sinner to be saved. Saved sinners are referred to as being in Christ. (Romans 8:1 There is therefore now no condemnation for those who are in Christ Jesus.) What has regeneration accomplished in the sinner? Paul tells us in 2 Corinthians 5:17 that a saved sinner is a new creation. The old has passed away and the new has come. Paul is talking about a drastic change in a person’s life that is wrought by the Holy Spirit in a person’s very soul. He has a new attitude, desires, likes, and dislikes. Old desires and old ways of relating to the world have passed away. Paul said “IF” anyone is in Christ he is a new creation. It then follows, if anyone is not a new creation and is completely unchanged by his profession of faith, then he is not in Christ and he is not saved because he has not been regenerated. A new Christian may be immature for a while, but this will not be a permanent condition because of the indwelling Holy Spirit. (2 Thessalonians 2:13 But we ought always to give thanks to God for you, brothers beloved by the Lord, because God chose you as the firstfruits to be saved, through sanctification by the Spirit and belief in the truth.) Believers are no longer enslaved by sin due to God’s work of regeneration and the indwelling Holy Spirit. The old has passed away. (Romans 6:6 We know that our old self was crucified with him in order that the body of sin might be brought to nothing, so that we would no longer be enslaved to sin.) God’s work of regeneration not only vanquishes the old, it brings in the new. (Romans 6:17-18 But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed, and, having been set free from sin, have become slaves of righteousness.)
A Christian is a new creation who has been changed from a slave of sin to a slave of righteousness by the awesome power of God. It is a power that does not fail. To assert that a Christian can be unchanged and remain a slave to sin is not only unbiblical, it insults God the Father, Son, and Holy Spirit!
Would anyone like to argue that regeneration is necessary, but may leave a true believer unchanged to wallow in his sin? Anyone?