Dīwān Rasāʾil al-Ṣābī, by Abū Isḥāq Ibrāhīm ibn Hillīl ibn Ibrāhīm ibn Zahrūn al-Kātib (384 AH./994 CE.)
(First paragraph) Books written in various periods of Islamic history are accepted as primary sources for their respective periods, notably those written by clerks (kātibs) of dīwāns and by persons who served in the state´s institutions or who were close friends with the senior officials of the state. These include letters written by ʿAbd al-Ḥamīd al-Kātib (d. 132/750), the clerk of Marwān II (127-132/744-750), the last Umayyad caliph; Ibn al-Muqaffāʾ, a witness of the transition period from the Umayyads to the ʿAbbāsids; Ibn al-Mowṣalāyā (d. 497/1104), who served as a man of letters (kātib) in Dīwān al-inshāʾ for over fifty years beginning from the era of al-Qāim bi-Amr Allāh (422-467/1031-1075) and Abū Isḥāq al-Ṣābī, a member of the al-Ṣābī family recognized in training adībs (literary men) and kātibs in the 4th/10th and the 5th/11th centuries.
Hachmeier, Klaus. Die Briefe Abū Isḥāq Ibrāhīm al-á¹¢ābiʾs (st.384/994 A.H./A.D.): Untersuchungen zur Briefsammlung eines berühmten arabischen Kanzleischreibers mit Erstedition einiger seiner Briefe. Hildesheim: Georg Olms, 2002.
———. “The Letters of Abū Isḥāq Ibrāhīm alá¹¢ābiʾ: A Large Buyid Collection Established from Manuscripts and Other Sources.” Mélanges de l’Université Saint-Joseph 63 (2010-2011): 107-221.