But when Peter came to Antioch, I opposed him to his face, because he stood condemned…he began to withdraw and hold himself aloof, fearing the party of the circumcision. Galatians 2:11-12
It was a dangerous time in the early church: everyone, including Peter, seemed to be moving away from God’s forgiveness, which is a free gift. But Paul remained dogmatic, and fought Peter publically over the issue.
Why do people run away from a free gift? This incident helps us understand this phenomena.