Romans 9:8 in the World English Bible
That is, it is not the children of the flesh who are children of God, but the children of the promise are counted as heirs.
Context
7 Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
8 That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed.
9 For this is the word of promise, At this time will I come, and Sara shall have a son.