Isaac was a child of promise because he was born to Sarah. The Galatians are likewise children of promise because they have been adopted to be part of God’s family (Galatians 4:1–7) through faith in Jesus Christ. They owe their spiritual existence as children of God to the promise of God1 that all those who have faith in Jesus Christ are sons of God and inheritors of the promises made to Abraham.
28 Now you, brothers, like Isaac, are children of promise.