Romans 9:8-12

That is, it is not the children of the flesh who are children of God, but the children of the promise are regarded as descendants. For this is the word of promise: “AT THIS TIME I WILL COME, AND SARAH SHALL HAVE A SON.” And not only this, but there was Rebekah also, when she had conceived twins by one man, our father Isaac; for though the twins were not yet born and had not done anything good or bad, so that God’s purpose according to His choice would stand, not because of works but because of Him who calls, it was said to her, “THE OLDER WILL SERVE THE YOUNGER.”