This means that children born by natural descent ⌞from Abraham⌟ are not necessarily God’s children. Instead, children born by the promise are considered Abraham’s descendants.
These people didn’t become God’s children in a physical way—from a human impulse or from a husband’s desire ⌞to have a child⌟. They were born from God.
Faith enabled Abraham to become a father, even though he was old and Sarah had never been able to have children. Abraham trusted that God would keep his promise.