Galatians 3:4 - Matthew Poole's English Annotations on the Holy Bible

There is no doubt but these churches in the regions of Galatia had their share in the sufferings of Christians by the Jews for their adherence to and profession of the doctrine of the gospel, which they might either wholly, or in a great measure, have avoided, would they have complied with the Jews in the observance of those legal rites. Therefore, (saith the apostle), to what purpose have you suffered so much for the owning of the Christian religion, if you now bring yourselves under the bondage of circumcision, and other legal observances? If it be yet in vain; by which words he either correcteth himself, as if he had said: But I hope better things of you, that I shall find that you did not suffer them in vain; or else he hinteth that their suffering so much would not be in vain, because, by their apostacy from the true faith for which they suffered, they would in effect deny it, as if it had been false, and their former suffering would rise up in judgment against them.