Abū Masʿūd, of the Dabbī tribe, hailing from Rayy and later settling in Isfahān.
He was born in the early 180s AH—during the caliphate of Hārūn al-Rashīd. From childhood he pursued knowledge, and while still a beardless youth was already counted among the ḥuffāẓ ⦗1⦘. He travelled in search of ḥadith to Iraq, Syria, the Ḥijāz, and Yemen, and caught up with the leading authorities of his time.
He heard ḥadith from: ʿAbd Allāh ibn Numayr; Abū Usāmah; Ḥusayn ibn ʿAlī al-Juʿfī; Abū Dāwūd al-Ḥafarī; Yazīd ibn Hārūn; Abū Dāwūd al-Ṭayālisī; Yaḥyā ibn Ādam; Jaʿfar ibn ʿAwn; Yaʿlā ibn ʿUbayd—and his brother Muḥammad ibn ʿUbayd; Azhar ibn Saʿd al-Sammān; Abū ʿĀmir al-ʿAqadī; ʿAbd al-Razzāq ibn Hammām; Shabābah ibn Sawwār; Ibn Abī Fudayk; Abū Aḥmad al-Zubayrī; Abū Bakr al-Ḥanafī; Wahb ibn Jarīr; Muḥammad ibn Yūsuf al-Firyābī; Muʾammal ibn Ismāʿīl; ʿUbayd Allāh ibn Mūsā; Abū Nuʿaym; ʿAffān; Abū Ṣāliḥ the scribe; Muḥammad ibn ʿĪsā ibn al-Ṭabbāʿ; Abū Jaʿfar al-Nufaylī; Abū al-Yamān; Abū ʿAbd al-Raḥmān al-Muqrī; al-Haytham ibn Jamīl; Abū al-Walīd; Muslim ibn Ibrāhīm—and many others.
His isnād extends even to such later teachers as Abū Bakr ibn Abī Shaybah, Muḥammad ibn Ḥumayd, and Bakr ibn Khalaf. A fascicle of his narrations, containing some of the loftiest chains, is still in circulation among students today.
Those who transmitted from him include: Abū Dāwūd—in his Sunan—Abū Bakr ibn Abī ʿĀṣim, Muḥammad ibn Yaḥyā ibn Mandah, Jaʿfar al-Firyābī, Muḥammad ibn al-Ḥasan ibn al-Muhallab, ʿAbd al-Raḥmān ibn Yaḥyā ibn Mandah (the brother of Muḥammad), and Aḥmad ibn Maḥmūd ibn Ṣabīḥ.
⦗1⦘ I.e., recognised as a master ḥadith memoriser at a remarkably young age.