Everyone who is "in Christ," through faith in His name, is a "new creation." We are new people. We are no longer who we were before we put our trust in the Lord Jesus. We are not the old person reformed or improved; we are a "new creation." Yes, we have the same body, but that is a mere tent in which we dwell. "For we know that if our earthly house, this tent, is destroyed, we have a building from God, a house not made with hands, eternal in the heavens" (2Co_5:1). Some day in glory, we will trade this temporal, earthly tent for an eternal heavenly one. Meanwhile, though we live in the same old tent we had in Adam, we are new tenants, a "new creation." We may have the same old physical brain, but we are learning to think an entirely new way. "We have the mind of Christ... be transformed by the renewing of your mind" (Rom_12:2 and 1Co_2:16). Christ lives in us, and His Spirit also dwells in us. His Spirit takes the word of God and unfolds the thinking of our Lord for us. As we embrace God's way of thinking more and more, we are transformed to walk in the newness that is ours in "in Christ."
In all the ways that matter before God, "old things have passed away; behold, all things have become new." The old guilt is replaced by new forgiveness. "There is therefore now no condemnation to those who are in Christ Jesus... in whom we have... the forgiveness of sins" (Rom_8:1 and Col_1:14).
The old foolishness is replaced by new wisdom. "For the wisdom of this world is foolishness with God... But of Him you are in Christ Jesus, who became for us wisdom from God" (1Co_3:19 and 1Co_1:30). The old unrighteousness is replaced with new righteousness. "All our righteousness are like filthy rags... For He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him" (Isa_64:6 and 2Co_5:21). The old hope of changing (self-help) is replaced by new hope of changing (sanctification, God changing us). "Cursed is the man who trusts in man and makes flesh his strength... You are in Christ Jesus, who became for us... sanctification" (Jer_17:5 and 1Co_1:30). This is grace upon grace. (Day by Day Grace)
It was of small importance in Paul’s eyes what his critics thought of him. He desired only to please his supreme Lord, whether he lived or died, was considered cold and staid or hot and impassioned. He was overmastered by his love of Christ. This may have been the sense of Christ’s love to his unworthy self, or the emotion that burned in his soul toward Christ, or the very love of Christ received into his heart, as a tiny creek on the shore receives the pulse of the ocean tide.
The Apostle had arrived at the deliberate conclusion and judgment that the “all” who realized what Christ had done for them (and he among them) must live with as much devotion toward Him as others toward themselves. A new world had been opened by Christ’s
resurrection. All things had become new. Let us live in daily touch with that world of faith and glory, refusing to be judged by the old standards. It is clear that the reconciliation of the world is as complete as God can make it, but it is for us to urge men to fall in with and accept God’s proposals.