Paul wants the Galatians to count the cost of what they are doing. When they first believed, they had "suffered so many things" for the gospel. If they now trade that gospel for the works of the law, all of that suffering would be wasted. Barnes points out that they "had suffered on account of their having embraced the gospel," not for keeping Jewish rites, so turning back would make their suffering pointless. Gill adds that "if such who have made a profession, and have suffered for it, should after all relinquish it, their sufferings for it are in vain."

Paul then adds, "if it be yet in vain." Both commentators read this as hope, not a final verdict. Barnes paraphrases it, "I trust it is not in vain," and Gill says that with these words the apostle "does, as it were, correct himself, and expresses his hope of them."

No reply from the Galatians is recorded. Paul answers in part himself with the words that close the verse: "if it be yet in vain." He will not yet say their suffering was wasted. He then moves straight to his next question: did the one who ministered the Spirit and worked miracles among them do it "by the works of the law, or by the hearing of faith?" (Galatians 3:5), and later he openly admits, "I stand in doubt of you" (Galatians 4:20).

Paul traveled through "the region of Galatia" and later returned there, "strengthening all the disciples" (Acts 16:6; Acts 18:23). The letter itself shows that following Christ crucified brought persecution: Paul asks why he still suffers persecution if he preaches circumcision (Galatians 5:11), and those pushing circumcision did so "lest they should suffer persecution for the cross of Christ" (Galatians 6:12). Gill says the Galatians had suffered reproach, afflictions, and persecutions for the sake of the gospel. The word "in vain" is the Greek eikē, meaning to no purpose, and Paul uses it twice in this short verse.

Paul shows that suffering for the gospel can be emptied of its fruit if a person walks away from the very gospel they suffered for. That is why he asks instead of simply warning. He wants the Galatians to remember what their faith already cost them and to see that the cross they suffered for is the same cross they are now setting aside (Galatians 3:1).

Paul's added words, "if it be yet in vain," show the heart of a pastor. He hopes the story is not finished. Galatians 6:9 holds out the same hope: "in due season we shall reap, if we faint not."