'Descendants' in the Bible

For the promise to Abraham or to his descendants that he would inherit the world was not through the law, but through the righteousness that comes by faith.

This is why the promise is by faith, so that it may be according to grace, to guarantee it to all the descendants—not only to those who are of the law but also to those who are of Abraham’s faith. He is the father of us all

He believed, hoping against hope, so that he became the father of many nations according to what had been spoken: So will your descendants be.

Neither are they all children because they are Abraham’s descendants. On the contrary, your offspring will be traced through Isaac.