The Galatian Churches listened to teachers who persuaded the Galatians to add circumcision, and perhaps some other items of the Law of Moses, to the good news about Jesus Christ.
However, Paul reminded the Galatians of how they acquired anything from God,
“Therefore He who supplies the Spirit to you and works miracles among you, does He do it by the works of the law, or by the hearing of faith?—just as Abraham ‘believed God, and it was accounted to him for righteousness’” (Galatians 3:5-6).
Paul asked a question, then helped them with the answer by reminding them that Abraham had righteousness accounted to him when he believed God, not when he did the works of the Law. Abraham preceded the Law, yet, he had faith and approval from God.
We have approval from God the same way. We believe Him, which leads us to do whatever He wants.