Galatians 2:18

“For if I build again the things which I destroyed, etc..] Which must be understood not of good things, for formerly he destroyed the faith of the Gospel, at least as much as in him lay, and now he built it up, established, and defended it; in doing which he did no evil, or made himself a transgressor, but the reverse; he showed himself a faithful minister of Christ: but of things not lawful, such as the rites and ceremonies of the law of Moses, which were now abrogated, and he had declared to be so all over the Gentile world; and therefore should he go about to establish these things as necessary to salvation, or teach men to join the observance of them with Christ's righteousness for…”

“Greek, "For if the things which I overthrew (by the faith of Christ), those very things I build up again (namely, legal righteousness, by subjecting myself to the law), I prove myself (literally, 'I commend myself') a transgressor." Instead of commending yourself as you sought to do (Gal 2:12, end), you merely commend yourself as a transgressor. The "I" is intended by Paul for Peter to take to himself, as it is his case, not Paul's own, that is described. A "transgressor" is another word for "sinner" (in Gal 2:17), for "sin is the transgression of the law." You, Peter, by now asserting the law to be obligatory, are proving yourself a "sinner," or "transgressor," in your having set it aside…”

“For if I build again the things which I destroyed - Paul here uses the first person; but he evidently intends it as a general proposition, and means that if anyone does it he becomes a transgressor. The sense is, that if a man, having removed or destroyed that which was evil, again introduces it or establishes it, he does wrong, and is a transgressor of the Law of God. The particular application here, as it seems to me, is to the subject of circumcision and the other rites of the Mosaic law. They had been virtually abolished by the coming of the Redeemer, and by the doctrine of justification by faith. It had been seen that there was no necessity for their observance, and of that Peter and…”

“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. Galatians 2:19”

“2:18 I am a sinner (or lawbreaker): Turning away from faith and back to the law brings a person under the jurisdiction of the law, where all stand under God’s judgment (Rom 3:10-12, 23-24; see Heb 6:1-8), and is itself a serious sin against Christ (Gal 5:2-4; cp. Heb 6:4-6). See also study note on 2:19. • if I rebuild: By insisting on keeping Jewish laws concerning food and circumcision (Gal 2:11-13). • Christ tore down the system of law through his death (Eph 2:14-16).”

“Gal 2:4, Gal 2:5, Gal 2:12-16, Gal 2:21, Gal 4:9-12, Gal 5:11; Rom 14:15; Co1 8:11, Co1 8:12 Galatians 2:19”