they are not all children of Abraham because they are Abraham's descendants. The promise was, In Isaac shall thy posterity be called.

Now if the first-fruits of the dough Abraham and the Patriarchs are holy, so also is the whole mass their descendants. And if the root of a tree Abraham is holy, so also are the branches his descendants.

This is why righteousness is of faith, that it may be a free gift; so that the promise stands firm to all Abraham's posterity; not to his children of his faith. For in the sight of the God in whom he believed, who gives life to the dead, and calls into being that which is not, Abraham is the father of us all both Jews and Gentiles,