From A Pastor's Heart

In Galatians 4, Paul is reminding his Galatian readers about how they came to know each other. More specifically, he is reminding them about their own kindness to him during a difficult time in his life and how they received him and the gospel of Jesus with honor. That, in turn, is part of his continuing encouragement to them: that they would rely solely on faith in Christ, and not on rituals or other works for their salvation.
Even though the Galatians have begun to rely on rituals and other works once again, Paul comes to them with concern and encouragement as he works to remind them that our salvation and freedom is based solely on Jesus Christ.