Thoughts from Martin Luther on Galatians 6:15

A new creation, by which the image of God is renewed (Col. 3:10), does not happen by the sham or pretense of some sort of outward works, because in Christ Jesus neither circumcision nor uncircumcision counts; but it is “created after the likeness of God in righteousness and holiness” (Eph. 4:24). When works are performed, they do indeed give a new outward appearance, which captures the attention of the world and the flesh. But they do not produce a new creation, for the heart remains as wicked and as filled with contempt of God and unbelief as it was before. Thus a new creation is a work of the Holy Spirit, who implants a new intellect and will and confers the power to curb the flesh and to flee the righteousness and wisdom of the world. This is not a sham or merely a new outward appearance, but something really happens. A new attitude and a new judgment, namely, a spiritual one, actually come into being, and they now detest what they once admired. Our minds were once so captivated by the monastic life that we thought of it as the only way to salvation; now we think of it quite differently. What we used to adore, before this new creation, as the ultimate in holiness now makes us blush when we remember it.
Therefore a new creation is nora change in clothing or in outward manner, as the monks imagine, but a renewal of the mind by the Holy Spirit; this is then followed by an outward change in the flesh, in the parts of the body, and in the senses. For when the heart acquires new light, a new judgment, and new motivation through the Gospel, this also brings about a renewal of the senses. The ears long to hear the Word of God instead of listening any longer to human traditions and notions. The lips and the tongue do not boast of their own works, righteousness, and monastic rule; but joyfully they proclaim nothing but the mercy of God, disclosed in Christ. These changes are, so to speak, not verbal; they are real. They produce a new mind, a new will, new senses, and even new actions by the flesh, so that the eyes, the ears, the lips, and the tongue not only see, hear, and speak otherwise than they used to, but the mind itself evaluates things and acts upon them differently from the way it did before. Formerly it went about blindly in the errors and darkness of the pope, imagining that God is a peddler who sells His grace to us in exchange for our works and merits. Now that the light of the Gospel has risen, it knows that it acquires righteousness solely by faith in Christ. Therefore it now casts off its self-chosen works and performs instead the works of its calling and the works of love, which God has commanded. It praises God and proclaims Him, and it glories and exults solely in its trust in mercy through Christ. If it has to bear some sort of evil or danger, it accepts this willingly and joyfully, although the flesh goes on grumbling. This is what Paul calls “a new creation.”