Muhammad ibn Umar al-Kashshi

Abū ʿAmr Muḥammad ibn ʿUmar ibn ʿAbd al-ʿAzīz al-Kashshī (أبو عمرو محمد بن عمر بن عبد العزیز الکَشّي), died 941 or 951 or 978, 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) called the Ikhtiyar ma'rifat al-rijal.

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), author of the Kitab al-Kafi. 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.

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), called the Ikhtiyar ma'rifat al-rijal. 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.