Galatians 3:4 “Have you suffered so much for nothing-- if it really was for nothing?”
“Have you suffered so much for nothing?” As in 3:2, Paul is appealing ot the Galatians’ personal experience in Christ before he delves into his theological arguments and defenses; as in verse 2, the ultimate underlying rhetorical question here is “Are all your experiences in the Kingdom of God a lie?” In verses 2 and 3, he appealed to the evidence of the work of the Holy Spirit in their lives. Here, the appeal is to suffering -- the suffering the Galatians had experienced for their faith, both individually and collectively.
There is no indication here, or anywhere else in the book, what this suffering consisted of. The narrative regarding Paul’s initial contact with the Galatians shows that originally, the people were deeply steeped in Greek native mythology (Paul and Barnabas had even been revered as human incarnations of Hermes and Zeus after performing miracles in the midst of the Galatian people – Acts 14:8-18). Later on, Jews who had tried to thwart Paul’s missionary work at earlier stops on the First Missionary Journey arrived and “won the crowd over.” (Acts 14:19a). This resulted in Paul being stoned and left for dead! (Acts 14:19b)! Thus, from the outset, the Galatian churches must have been plagued with pressures from the outside, particularly involving pious Jews who saw this "new religion "as a threat. Whether the pressure came from the worshippers of Zeus, devout Jews, or the Roman authorities, there were powerful anti-Christian forces at play in Galatia.
I think therefore we can presume this “suffering” involved persecution of some type. It must have been severe, or Paul would not have noted it like this.
“If it really was for nothing.” Obviously, the persecution must have brought forth a great deal of fruit – the “furnace” forged a mighty work. Otherwise, this argument wouldn’t mean much. If the Galatians had gone through so much, and those difficulties had lead to so much good, to so much growth in God's Kingdom, how could they just “chuck it all” and give in to the source of that persecution (the Jews in the area, I presume, from the Acts 14 account)? Verses 2-5 combine together to show that a changed life really is one of the best arguments for salvation by faith!!