Ibn Kathir set out his hierarchy of interpretation in the commentary's introduction, drawing on the principles of his teacher Ibn Taymiyya. The soundest explanation of a verse is another verse, since the Quran, in this view, comments on itself, stating briefly in one place what it unfolds in another. Where Scripture is silent, the interpreter turns to the sunnah of the Prophet, which the commentary treats as the Quran's authorised exposition; where the sunnah too is silent, to the understanding of the companions, who witnessed the revelation's circumstances; and after them to the successors, with disagreements noted and weighed. What distinguishes the work in practice is the author's training as a hadith critic. Reports are not merely gathered, as the older archive commentaries had gathered them, but graded, and material judged weak is flagged or dropped.
Ibn Kathir is notably wary of the Israiliyyat, the narratives absorbed from Jewish and Christian tradition that earlier commentators had transmitted freely; he sorts them into the acceptable, the false and the unverifiable, and counsels silence over the last. The result is leaner than al-Tabari and more homiletically direct, a commentary built for readers who want the received meaning with its evidence, and its combination of rigour and accessibility explains its immense modern circulation, including in abridged and translated forms.