Galatians 3:1-5 justification by the works or those who preach the doctrine of faith?

Several things made the folly of the Galatian Christians worse. They had the doctrine of the cross preached, and the Lord's supper administered among them, in both which Christ crucified, and the nature of his sufferings, had been fully and clearly set forth. Had they been made partakers of the Holy Spirit, by the ministration of the law, or on account of any works done by them in obedience thereto? Was it not by their hearing and embracing the doctrine of faith in Christ alone for justification? Which of these had God owned with tokens of his favour and acceptance? It was not by the first, but the last. And those must be very unwise, who suffer themselves to be turned away from the ministry and doctrine which have been blessed to their spiritual advantage. Alas, that men should turn from the all-important doctrine of Christ crucified, to listen to useless distinctions, mere moral preaching, or wild fancies! The god of this world, by various men and means, has blinded men's eyes, lest they should learn to trust in a crucified Saviour. We may boldly demand where the fruits of the Holy Spirit are most evidently brought forth? whether among those who preach justification by the works of the law, or those who preach the doctrine of faith? Assuredly among the latter.

The apostle is here dealing with those who, having embraced the faith of Christ, still continued to seek for justification by the works of the law; that is, who depended upon their own obedience to the moral precepts as their righteousness before God, and, wherein that was defective, had recourse to the legal sacrifices and purifications to make it up. These he first sharply reproves, and then endeavours, by the evidence of truth, to convince them. This is the right method, when we reprove any for a fault or an error, to convince them that it is an error, that it is a fault.