This is the question that the apostle Paul asks in verse 19, both for the purpose of anticipating the objections of the Antinomians, and also that he may the more emphatically show the place of the law in the Gospel. The question is a very natural one. Since the inheritance is wholly by promise, and a covenant confirmed can not be changed,—nothing can be taken from it, and nothing added to it,—why did the law come in four hundred and thirty years afterward? “Wherefore then serveth the law?” More literally, Why then the law? What business has it here? What part does it act? Of what use is it? GTI 136.1