The testimony of the Apostle Paul was “If any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new” (2 Cor. 5:17).
When a person comes to personally know Jesus Christ as their Savior, God inwardly transforms their life. He gives them a new nature—the nature of Christ—for all believers have become “partakers of the divine nature” (2 Pet. 1:3-4). This new nature naturally produces new attitudes and opinions, new likes and dislikes, new loves and hatreds. The things a person once loved, they now hate; and the things they once hated, they now love. The whole inward motivation of their life has been changed.
Not only is this change apparent to the inner consciousness of the individual, their outward life will also appear different to those around them. Their whole character of life will be changed. Often a complete change of disposition will occur and even one’s conversation may be altered.
When a person has accepted Christ, there will be changes within them, particularly in their desires. Their ambitions, affections and inward nature, will have switched from evil things to godliness. If we can honestly say that such a change has taken place in our life, we may rest assured that it was accomplished by the Holy Spirit, and is a sign that we have been born of God (John 1:12,13).
When a person becomes a Christian, they are “born again” (3:3). Human birth is the demonstration of physical life. The new birth is the demonstration of spiritual life—the evidence of the work of the Holy Spirit. When a person is born again, they receive a new inner nature (2 Cor. 5:17).
The consciousness of a new nature—the Christ life—within is evidence that we are born of God. Of course, the old nature is also within, and conflicts often arise between the old and the new natures. “The flesh lusts against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that you cannot do the things that you would” (Gal. 5:17). Your old nature (“the flesh”) fights with the new nature (“the Spirit”). Such conflicts are normal in the life of a real Christian—one who has been saved and made a child of God forever.