Bahrām al-Marwazī, a native of Marw who later made his home in Naysābūr.
He was born sometime after 170 AH.

He studied under Sufyān ibn ʿUyaynah, Wakīʿ ibn al-Jarrāḥ, al-Naḍr ibn Shumayl, Yaḥyā ibn Saʿīd al-Qaṭṭān, Muʿādh ibn Hishām, Abū Usāmah, ʿAbd al-Raḥmān ibn Mahdī, ʿAbd Allāh ibn Numayr, Muḥammad ibn Bakr al-Bursānī, ʿAbd al-Razzaq, Muḥammad ibn Yūsuf al-Firyābī, ʿAffān, and a large number of others.

He pursued knowledge assiduously, recorded it, excelled in it, and his reputation spread far and wide.

Those who transmitted from him include the compilers of the canonical collections—except Abū Dāwūd—as well as Abū Zurʿah al-Rāzī, Abū Bakr ibn Khuzaymah, Abū al-ʿAbbās al-Sarrāj, Muʾammal ibn al-Ḥasan al-Māsarjisī, Aḥmad ibn Ḥamdūn al-Aʿmashī, Muḥammad ibn Aḥmad ibn Zuhayr, and many others.

Al-Ḥākim Abū ʿAbd Allāh said: “Abū Yaʿqūb al-Kawsaj was born in Marw, raised in Naysābūr, left offspring, and there he passed away. He was one of the leading imams among the scholars of hadith, renowned for his asceticism and firm adherence to the sunnah. The authors of the two Ṣaḥīḥs relied upon him without reservation. He is also the compiler of the Questions put to Aḥmad ibn Ḥanbal—a work belittled by the innovators and the reckless.”

I heard Abū al-Walīd Ḥassān ibn Muḥammad, the jurist, say:
“I heard our shaykhs mention that when news reached Isḥāq ibn Manṣūr that Aḥmad ibn Ḥanbal had revised his position on some of the issues Isḥāq had recorded from him, Isḥāq placed the notebook in a satchel, slung it over his back, and set out on foot (1) to Baghdad, presenting Aḥmad’s own handwritten answers to him on every single question…"