Galatians 2:18 - Wesley's Explanatory Notes

By no means. For if I build again — By my sinful practice. The things which I destroyed — By my preaching, I only make myself — Or show myself, not Christ, to be a transgressor; the whole blame lies on me, not him or his gospel. As if he had said, The objection were just, if the gospel promised justification to men continuing in sin. But it does not. Therefore if any who profess the gospel do not live according to it, they are sinners, it is certain, but not justified, and so the gospel is clear.