In turning from the plain truth of Jesus Christ as crucified for sin, though having begun by believing the Gospel message, Christians can be found soon resorting to “Law keeping” as the means of continued growth in Christ. At this sort of thing, St. Paul was so absolutely astounded that he was nearly at a total loss as to what to say! “You fools, who has beguiled you?”
The apostolic inquiry:
On what basis does God give you spiritual strength, working mightily among you?
a) Works: performance (an obedience of Christians to the Law)
b) Faith: believing and relying upon the Gospel (the obedience of Christ to the Law)