Someone who has been born again, by the Holy Spirit, has been changed in spirit. He is a new creation, born of God by incorruptible seed; however, he still has his flesh with him, and in that there is no good thing.
Until our bodily resurrection, the flesh does not, and cannot, improve; it is continually full of nothing good. Our born again human spirit is continually in holiness and love; and, our soul (habits of desire and thought) is the battleground between them.
A genuine Christian is characterised by a righteous life; but, because of his ever-present flesh, he cannot live a life completely free of sin. That is one reason why this corruptible must put on incorruption, in the resurrection.
