Romans 9:8-10

New Revised Standard Version, Anglicised Catholic Edition

⁸ This means that it is not the children of the flesh who are the children of God, but the children of the promise are counted as descendants. ⁹ For this is what the promise said, ‘About this time I will return and Sarah shall have a son.’ ¹⁰ Nor is that all; something similar happened to Rebecca when she had conceived children by one husband, our ancestor Isaac.