Some Jewish Christians taught in the Galatian churches that everyone had to observe the Mosaic Law in order to be accepted by God as approved (righteous). Paul, however, wrote this letter to contend that God's acceptance and approval (righteousness) comes by grace through faith in the finished work of Jesus on the cross, not by works of the Mosaic Law.

God's approval and acceptance of us is not based on how well we keep the law (save ourselves), but purely an underserved gift from God (God saves us). Nonetheless, we all have a tendency to seek righteousness by law (try to save ourselves) instead of grace (receive salvation from God). And this tendency is how we pervert the gospel.