Legalism: treating that which is good as though it were essential. The Galatian believers took circumcision and made it essential in the life of a believer. Paul told them if they did this (i.e. look to circumcision as something that enhances their relationship with God), Christ will be of no value to them (5:2). This messages challenge: keep the main thing the main thing. Keep that which is essential (salvation through Jesus by faith alone) as the main thing.