or al-Azharī from al-Khaṭīb, the second form is that the narrator is higher in scholarly standing—for example, when a ḥāfiẓ (hadith master) narrates from his shaykh, such as Mālik narrating from ʿAbd Allāh ibn Dīnār; the third unites both considerations, as in ʿAbd al-Ghanī narrating from al-Ṣūrī, or al-Barqānī from al-Khaṭīb. Included here as well are instances of Companions transmitting from Successors, such as the four ʿAbd Allāhs and others reporting from Kaʿb al-Aḥbār; and cases in which a Successor relates from a contemporary Successor, as al-Zuhrī and al-Anṣārī relate from Mālik. As for ʿAmr ibn Shuʿayb, he himself was not a Successor, yet more than 20—some say more than 70—of them narrated from him. Allah knows best.

Forty-Second Category:
The mudabbaj – reciprocal narration between contemporaries

Two qarīnān (“contemporaries”) are those who are close to each other in age and in their chains of transmission, although al-Ḥākim at times considered proximity in isnād alone sufficient. When each of the two narrates from the other—such as ʿĀʾishah and Abū Hurayrah, or Mālik and al-Awzāʿī—the narration is termed mudabbaj. Allah knows best.

Forty-Third Category:
Identifying brothers

This is one of their specialized subjects. Ibn al-Madīnī devoted a monograph to it, followed by al-Nasāʾī, then al-Sarrāj and others. An example of brothers among the Companions is ʿUmar and Zayd, the sons of al-Khaṭṭāb, and ʿAbd Allāh and ʿUtbah, the sons of Masʿūd.