'Forefather' in the Bible

What then can we say that Abraham, our physical ancestor, has found?

Before, not after. And he received circumcision as a sign, a mark attesting the reality of the faith-righteousness which was his while still uncircumcised, that he might be the forefather of all those who believe even though they are uncircumcised--in order that this righteousness might be placed to their credit;

and the forefather of the circumcised, namely of those who not merely are circumcised, but also walk in the steps of the faith which our forefather Abraham had while he was as yet uncircumcised.

so that the promise should be made sure to all Abraham's true descendants; not merely to those who are righteous through the Law, but to those who are righteous through a faith like that of Abraham. Thus in the sight of God in whom he believed, who gives life to the dead and makes reference to things that do not exist, as though they did, Abraham is the forefather of all of us. As it is written, "I have appointed you to be the forefather of many nations."

Under utterly hopeless circumstances he hopefully believed, so that he might become the forefather of many nations, in agreement with the words "Equally numerous shall your posterity be."

And not only that, but also Rebekah received a promise when she became pregnant by one man, our ancestor Isaac.