For if they, who are of the law, be heirs: faith is made void, the promise is made of no effect. That is, if the Jews, who are under the law, are the only heirs of the blessings promised, it will follow that the faith which Abraham had before the circumcision, and before the law, was of no value, which I have shown to be false. And, secondly, it will follow that the promise made to him, that in him all nations should be blessed, is also null. (Witham)
To prevent anyone from saying that it is possible to have faith and to keep the law at the same time, Paul shows that this is impracticable. For one who clings to the law as if it were of saving force dishonors the power of faith. This is why Paul says that faith is made void, i.e., that there is no need of salvation by grace…. And without faith, there is no promise of inheritance, which is what scared the Jews most of all, because that is what they really wanted. For the promise was that they should be heirs of the entire world.
