This man (1) was the imam, hadith master, erudite scholar, and foremost traditionist of al-Andalus: Abū Muḥammad al-Qurṭubī, a client of the Banū Umayyah.

He studied under Baqī ibn Makhlad, Muḥammad ibn Waḍḍāḥ, Aṣbagh ibn Khalīl, Muḥammad ibn ʿAbd al-Salām al-Khushanī, and a number of other Andalusian scholars; Muḥammad ibn Ismāʿīl al-Ṣāʾigh and his contemporaries in Mecca; Muḥammad ibn al-Jahm al-Sammārī; Abū Muḥammad ibn Qutaybah; Jaʿfar ibn Muḥammad ibn Shākir; Abū Bakr ibn Abī al-Dunyā; al-Ḥārith ibn Abī Usāmah; Muḥammad ibn Ismāʿīl al-Tirmidhī; Ismāʿīl al-Qāḍī—from whom he transmitted extensively; Abū Bakr ibn Abī Khaythamah—from whom he copied his History; Ibrāhīm ibn ʿAbd Allāh al-Qaṣṣār, the companion of Wakīʿ in Kūfa; and many others besides.

He did not have the opportunity to study with Abū Dāwūd, so he compiled a Sunan patterned on Abū Dāwūd’s Sunan. Likewise, he lacked access to Ṣaḥīḥ Muslim, so he produced a Ṣaḥīḥ arranged on the same model. He also authored Kitāb Birr al-Wālidayn (Filial Piety toward Parents), the Musnad of Mālik, al-Muntaqā fī al-Āthār (The Selected Traditions), Kitāb al-Ansāb (Genealogies)—a work of striking elegance—and other books.

Those who narrated from him include his grandson Qāsim ibn Muḥammad, ʿAbd Allāh ibn Muḥammad al-Bājī, ʿAbd Allāh ibn Naṣr, ʿAbd al-Wārith ibn Sufyān, the judge Muḥammad ibn Aḥmad ibn Mufarrij, Abū ʿUthmān Saʿīd ibn Naṣr, Aḥmad ibn al-Qāsim al-Ṭāhartī, Qāsim ibn Muḥammad ibn ʿAslūn, Abū ʿUmar Aḥmad ibn al-Jasūr, and a multitude of others.

The loftiest chains of transmission in al-Andalus ended with him, coupled with prodigious memory, exactitude, eloquence in Arabic, pre-eminence in issuing legal verdicts, flawless dignity, and imposing stature.

More than one scholar praised him, and the writings of Ibn Ḥazm, Ibn ʿAbd al-Barr, and Abū al-Walīd al-Bājī are replete with the narrations of Qāsim ibn Aṣbagh.