Paul now shows that if justification is by faith alone, it cannot also be by the law because the justification that the law provides operates on an entirely different basis. The law demands good works, but faith says nothing whatsoever about good works as the quotation from Habakkuk proves.
Was the covenant made through Moses with Israel a gracious covenant or a legal covenant? Quite clearly Paul understood it to be a legal covenant, a covenant of works, for the terms of its blessing were based on human works: ‘The man that doeth them shall live in them.’ The law is not of faith, and therefore it is not of grace. It has nothing to do with the terms of the promise made to Abraham for the promise brings blessing, but the law brings only a curse, because those under its works inevitably fail to do those works and therefore bring its uncompromising penalty down upon them.