Abraham and his family received a promise that he would inherit the world, but that wasn’t because he obeyed the law. It was because of his faith, which made him right with God.
In other words, God’s children aren’t all those who are physically descended from Abraham. Rather, they’re the children God promised to him. Those are the ones who are considered to be Abraham’s children.
And Abraham is also the father of those who are circumcised, but who aren’t just circumcised—they also follow in the steps of our father Abraham, who had faith before he was circumcised.
Melchizedek didn’t trace his family line from Levi, but he still collected a tenth from Abraham. Melchizedek blessed the one who had received the promises.
By faith Noah, out of great respect for God, built an ark to save his family after God warned him about things that could not yet be seen. By doing this Noah showed the world that it was guilty, but he was considered right with God because of his faith.