Romans 9:8-9 “It is not the natural children who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring. For this was how the promise was stated: ‘At the appointed time I will return, and Sarah will have a son.’”

We become God’s children by the power of God’s promise. This is how it was in Abraham’s own family. You may know that Abraham and Sarah had difficulty having children, but Abraham had a number of sons. Without any miraculous help, Abraham fathered a son Ishmael with the family servant Hagar. Ishmael was a “natural son.” But he and his descendants were not children of God.

After Abraham’s wife Sarah died, he married another woman, Keturah. Together they had six sons. We don’t know much about the men themselves, but later on their descendants, too, were not genuine children of God.

Abraham and Sarah had one son, Isaac. Isaac’s very existence was owed to the power of God’s promise. Isaac was a “miracle baby,” because Sarah was naturally unable to conceive. At the time she became pregnant with Isaac she was well past menopause. It was only the power of God’s word, God’s promise, that enabled Sarah to conceive. Isaac came from God’s promise as much as he came from his physical parents.

Paul is using this story as an illustration and example of what makes a person a true child of God. There is a miracle of God’s promise involved. God’s promises create another miracle birth. They give birth to faith, a living trust and hope in God. That is what made Abraham different.

Five chapters earlier Paul quoted this description of Abraham from Genesis 15, “Abraham believed God, and it was credited to him as righteousness.” This is what made Abraham a forgiven child of God. It works the same for us. In his first letter the Apostle Peter tells us, “You have been born again… through the living and enduring word of God.”

God comes to us with a promise: “Your sins are all forgiven for the sake of Jesus’ death on the cross.” And faith stirs inside us. Like Abraham, we believe the God who forgives our sins and credits us sinners as righteous people. Like Abraham, we are God’s children because we are children of the promise.