Did you suffer so many things in vain—if indeed it was in vain?
4. Have ye suffered so many things? This is another argument. Having suffered so many things in behalf of the gospel, would they now, in an instant, lose it all? Nay, he puts it in the way of reproach, if they were willing to lose the advantage of so many illustrious struggles which they had made for the faith.
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.
Commenting on Galatians 3:1-5
Have ye suffered so many things in vain?.... These Galatians had suffered great reproach, many afflictions and persecutions for the sake of the Gospel, as all that embrace it must expect to do; and which to them that persevere in the faith of the Gospel will not be in vain, they will be followed with eternal life and glory; not that these things are meritorious...