The letter to the churches of Galatia, written by the apostle Paul, was sent to correct two forms of error creeping into the churches.
The first form was that obedience to the law, mingled with faith, was the ground of the sinner’s justification. In other words, to be a Christian one must also follow the Law of Moses. The second error was that the Christian is made perfect by keeping the Law.
Both are incorrect and Paul meets these errors head on. He made it clear that it is the gospel of grace that saves us. The gift of the Spirit is by faith, not by works of the law. Paul marveled the churches had abandoned this truth.