Treasury of Scripture Knowledge
Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all,
but by his mercy they are made upright for nothing, by the deliverance secured through Christ Jesus.
So as we have been made upright by faith, let us live in peace with God through our Lord Jesus Christ,
So you see, the real descendants of Abraham are the men of faith.
he made us, dead as we were through our offenses, live again with the Christ. It is by his mercy that you have been saved.
so that we might be made upright through his mercy and become possessors of eternal life in fulfilment of our hope.
For when God made his promise to Abraham, since there was no one greater for him to make oath by, he did so by himself,
2 Peter 1:10
Therefore, brothers, make all the greater efforts to make God's call and choice of you certain. For if you have these qualities, you will never stumble,
and he was afterward given the mark of circumcision as the stamp of God's acknowledgment of the uprightness based on faith that was his before he was circumcised, so that he should be the forefather of all who, without being circumcised, have faith and so are credited with uprightness,
That is to say, it is not his physical descendants who are children of God, but his descendants born in fulfilment of the promise who are considered his true posterity.