Romans 9:7-9

New Revised Standard Version Catholic Edition

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