17. The reason the Gospel has the efficacy ascribed to it in the preceding verse is not because of its pure morality, or because it reveals and confirms a future state of retribution, but because it reveals a righteousness from God. As this is one of those expressions which convey ideas unique to the Gospel, its meaning is to be learned not merely from the meaning of the words, but from parallel passages and from the explanations given in the Gospel itself of the whole subject to which it relates.