A 9th-century Description
This passage is from Yaʿqubi, an Arab bureaucrat who lived in the 9th century. He describes the ʿAbbasid claim to Damascus, in what was Umayyad heartland of Syria. ʿAbdallah b. ʿAli was the uncle of the first ‘Abbasid caliph Saffah.
This passage, also from Ya’qubi, is about Sulayman b. Hisham, the son of one of the Umayyad caliphs, and what happens when he approaches the first ‘Abbasid caliph Saffah (here: Abu l-‘Abbas).
Source, pp. 1084-5, then 1087-8.