If I witness a miracle, was it through law-keeping or through faith?
Any miracle you witness is not through law-keeping but through faith. The Law could not perform miracles; it was impossible. The Holy Spirit, activated by faith, works among believers and transforms them. Grace comes by faith plus nothing, never by works religion.
Les explains that Paul asks whether the One who ministers the Spirit and works miracles among them does it by the works of the Law or by the hearing of faith. The Law could not perform any miracles; it was impossible. But when the Holy Spirit activated the hearts and minds of the pagan Galatians and others throughout the Roman Empire, the result was a miraculous transformation from paganism, idolatry, and immorality. They stepped into a whole new lifestyle—a miracle in itself. There may have been other manifestations of the miraculous in the early church, though Paul does not explicitly delineate them. Les says the question remains the same: if you have witnessed a miracle, was it through keeping the Law or through the manifestation of the Spirit activated by faith? The answer is faith, plus nothing. Les emphasizes that we are not under Law but under grace, and we come under grace and out from under the Law by faith. The theme of Galatians is not to be suckered into a works religion, but to maintain that we are saved by grace through faith, plus nothing.