The plan of salvation foretold by the sacred authors, recounted and explained by them, is found as the true word of God in the books of the Old Testament: these books, therefore, written under divine inspiration, remain permanently valuable. "For all that was written for our instruction, so that by steadfastness and the encouragement of the Scriptures we might have hope" (Rom. 15:4).
Mpango wa wokovu uliotabiriwa, ukasimuliwa na kuelezwa na watunzi watakatifu, unajitokeza (exstat) kama Neno la kweli la Mungu katika vitabu vya Agano la Kale. Ndiyo sababu vitabu hivyo vilivyoandikwa kwa uvuvio wa kimungu vinahifadhi thamani ya daima: “Kwa kuwa yote yaliyotangulia kuandikwa yaliandikwa ili kutufundisha sisi; ili kwa saburi na faraja ya Maandiko tupate kuwa na tumaini” (Rum 15:4).