Muhammad ibn Umar al-Kashshi
Abū ʿAmr Muḥammad ibn ʿUmar ibn ʿAbd al-ʿAzīz al-Kashshī (), 854–941/951 CE, known as al-Kashshi or (in Persian) as Kashshi, was a Twelver Shi'ite scholar specializing in biographical evaluation () and hadith studies. He is the author of the , a major biographical work which ranks as one of the four main sources in the Shi'ite literature. Al-Kashshi's original work is now lost, but parts of it survive in an abridgement made by Shaykh Tusi (995–1067 CE) called the . Life. Al-Kashshi's exact date of birth is unclear. However, he is known to  have been a contemporary of Muhammad ibn Ya'qub al-Kulayni (864–941 CE), author of the . Al-Kashshi and al-Kulayni shared a number of teachers such as Muhammad ibn Ismail al-Naysaburi, as well as some students such as Ibn Qulawayh. This would place al-Kashshi roughly in the same time period as al-Kulayni, i.e., somewhere between the middle of the 9th century and the middle of the 10th century CE. He was born in city of Kesh or Kish (known today as Shahrisabz) in Transoxiana (today: Uzbekistan). Writings. Al-Kashshi's works are all lost today. However, one  work known as the survives in an abridgement made by Shaykh Tusi (995–1067 CE), called the . This work deals with the biographical evaluation of hadith transmitters, the goal of which was to establish whether individual transmitters are to be regarded as trustworthy, and whether their narrations –one of the main sources of Islamic doctrine– should be accepted or rejected. The ranks as one of the four most important works in the Shi'ite biographical () literature.