Carson on the Transformed Life

D. A. Carson writes (Still Sovereign, Baker, 259):

One must not conclude…that new covenant believers are anywhere promised moral and spiritual perfection this side of the new heaven and the new earth. Nevertheless, both the Old Testament prophecies regarding the new covenant and the age of the Spirit, and the New Testament claims regarding their fulfillment, lead us to expect transformed lives. Indeed, it is precisely this unequivocal expectation that authorizes Paul to set up the tension we have already noted: the exhortations to live up to what we are in Christ are predicated on the assumption that what we are in Christ necessarily brings transformation, so that moral failure is theologically shocking, however pragmatically realistic it may be. Indeed, it might be argued that this accounts for some of the tension in 1 John….It is worth recalling John’s insistence that believers do sin, and people who claim they do not are liars, self-deluded, and guilty of charging God with falsehood (1 John 1:6-10). At the same time, he repeatedly insists that sinning is not done among Christians. Various explanations have been advanced, but the most obvious is still the best: although both our experience and our location between the “already” and the “not yet” teach us that we do sin and we will sin, yet every single instance of sin is shocking, inexcusable, forbidden, appalling, out of line with what we are as Christians.