For the promise to Abraham or to his descendants that he would be heir of the world was not through the Law, but through the righteousness of faith.

For if those who are of the Law are heirs, faith is made void and the promise is nullified;

For this reason it is by faith, in order that it may be in accordance with grace, so that the promise will be guaranteed to all the descendants, not only to those who are of the Law, but also to those who are of the faith of Abraham, who is the father of us all,

yet, with respect to the promise of God, he did not waver in unbelief but grew strong in faith, giving glory to God,

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.”