If we are not led by the Spirit into the kingdom of Christ then we are eo ipso in the kingdom of Satan, and then one’s whole empirical piety is nothing other than condemned works of the law. Man is flesh, and in the flesh there is nothing which is not judged. The righteousness which counts before God is not man’s real piety but Christ’s alien righteousness. The new man which is born anew by water and the Spirit is that man who in faith takes refuge in Christ. It is not the converted man in his empirical piety.
But simultaneously the older Luther also speaks just as strongly as the younger Luther about a progress in sanctification, a constant struggle against sin, as an increasing cleansing and expulsion of sin. The growth of this sanctification is the Spirit’s work. The man who by faith in Christ is Spirit, is simultaneously flesh by virtue of his self. And that is as totus homo. The old man, the flesh, is not merely the “lower” part of man (the real self minus the empirical piety); but it is man in his totality. The struggle in man is therefore not a struggle between a higher and lower part of man’s nature, but between man’s real self and the Spirit of God. Therefore, that which the struggle is against is our total real self, and that which fights it is the Spirit. Thus the two apparent contradictory sentences from 1 John are both true: “No one born of God makes a practice of sinning, for God’s seed abides in him, and he cannot keep on sinning because he has been born of God” (1 John 3:9). “If we say we have no sin, we deceive ourselves, and the truth is not in us” (1 John 1:8). There will always be a real self for the Spirit to fight no matter how pious it might otherwise be. Christ’s alien righteousness, to which faith clings, may of course cover all the remaining sin, so that it is no longer attributed to one. But it does not destroy the remaining sin as a reality. The sin as a reality is remaining. Justification therefore means that war is declared upon the remaining sin. The beginning of its expulsion starts in justification. But this expulsion of sin is only in its beginning in this life. Only in the resurrection will it be completely finished.
It is the Spirit which expels sin by the Word about the forgiveness of sin, not man’s increasing empirical piety. Expulsion of sin is therefore not as a matter of course identical with a psychologically noticeable and therefore unmistakable increase of empirical piety. On the contrary, the sin which is to be expelled comprises the total man. It presupposes a real sinner when we speak of sanctification, that is a total sinner, not one who by virtue of a visibly increasing empirical piety is just partly a sinner. The expulsion of sin is that destruction of the power of sin which is a result of the fact that we as total sinners are brought into Christ’s kingdom. As it is clearly stated in the explanation to Luther’s Small Catechism, the expulsion of sin is this, that the Spirit daily works penitence through the law and faith through the gospel. This is a daily repetition of penitence wrought by the law and of faith wrought by the gospel. The Spirit mediates a daily repetition of Christ’s death and resurrection in us, not an evolution of our indwelling religious and moral strength by which the meaner tendencies in us are being checked. Luther therefore says that the Spirit, as long as sin is not completely expelled (and this does not take place before the last day), has not been given us in a full measure but only as first fruits. That the Spirit is an eschatological category or concept, which was clearly evident in the young Luther, is now even more clear. The powers of the world to come are by the Spirit active in the midst of the world of sin and death. But inasmuch as sin and death are constant realities, the Spirit is only given us as first fruits.
Regin Prenter, “Spiritus Creator”, pages 224-226