Romans 9:7-9

New Revised Standard Version, Anglicised Catholic Edition

⁷ and not all of Abraham’s children are his true descendants; but ‘It is through Isaac that descendants shall be named after you.’ 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.’