He inclined toward the Kūfan school of grammar and even authored a book on the subject. His memory was prodigious in the fields of historical reports, biography, Qur’an commentary, and poetry. He was an eloquent orator, a smooth-tongued poet, gifted in epistolary prose and rhetoric, pious, and stern in judgment. He was appointed judge of Hīt (1) and al-Anbār in the year 276 AH, and afterwards judge over parts of al-Jabal.

Judge Abū Naṣr Yūsuf ibn ʿUmar said: “I used to accompany my father to the palace of the Caliph al-Muqtadir, where he was deputizing for his own father, the judge Abū ʿUmar. There I would see the judge Abū Jaʿfar; my father would sit with him and the two would exchange knowledge until a number of servants gathered around them. I heard Abū Jaʿfar say, ‘I have committed to memory fifteen thousand lines of my own poetry (2), and for the benefit of others I know many times that number.’

Judge Abū Ṭālib Muḥammad, son of the judge Abū Jaʿfar, related: “I was with my father at a funeral, and by his side was Abū Jaʿfar al-Ṭabarī. My father began exhorting and consoling the bereaved; al-Ṭabarī joined in and added his own words (3). The conversation broadened between them, branching into topics that delighted everyone present, and the day grew long. When we rose to leave, my father said to me, ‘My son, who was that shaykh?’ I replied, ‘That was Muḥammad ibn Jarīr al-Ṭabarī.’ He exclaimed, ‘We belong to Allah! I did not conduct myself with him as I ought—why did you not tell me? Had I known, would I have engaged him in that same sort of discussion?’”