thirty years (1).

As for his work al-Mujarrad fī Asmāʾ Rijāl Kitāb Sunan al-Imām Abī ʿAbd Allāh Ibn Mājah, he divided it into eight strata, each named after leading authorities, except for the stratum of the Companions (2). The remaining seven strata are: the stratum from the era of al-Aʿmash and Ibn ʿAwn (3); the stratum of al-Zuhrī and Ayyūb (4); the stratum of Ibn al-Musayyib and Masrūq (5); the stratum of al-Ḥasan and ʿAṭāʾ (6); the stratum of ʿAffān and ʿAbd al-Razzāq (7); the stratum of ʿAlī ibn al-Madīnī and Aḥmad ibn Ḥanbal (8); and the stratum of al-Bukhārī and those who remained (9). It is clear that these strata, too, ignore chronological order.

By contrast, al-Dhahabī fixed a stratum at ten years in his monumental Tārīkh al-Islām, producing a total of seventy strata. Does this mean that, in that book, he laid down an explicit chronological limit for the stratum that differs from his practice elsewhere? To the best of our knowledge, no one before him had attempted such an arrangement.

Al-Dhahabī’s procedure has led some historians to claim that he diverged from the earlier scholars—and even from his own practice in his other writings (10).

Yet our comprehensive study of Tārīkh al-Islām shows that here he intended by “stratum” nothing other than a ʿaqd, that is, a concept denoting a unit