Ridda wars
Sayf ibn Umar al-Usayyidi al-Tamimi () was an early Islamic historian and compiler of reports who lived in Kufa. He wrote "Kitāb al-futūh al-kabīr wa 'l-ridda", which is al-Tabari's main source for the Ridda wars and early Muslim conquests. It also contains important information on the structure of early Muslim armies and government. According to al-Dhahabi, Sayf died during the reign of Harun al-Rashid (786-809).