Here follows the biography of al-Maʾmun (1):

He is ʿAbd Allah al-Maʾmun ibn Hārūn al-Rashīd ibn Muḥammad al-Mahdī ibn Abū Jaʿfar al-Manṣūr ʿAbd Allah ibn Muḥammad ibn ʿAlī ibn ʿAbd Allah ibn ʿAbbās, a Qurashī, Hāshimī, ʿAbbāsid; kunya Abū Jaʿfar, the Commander of the Faithful [al-Maʾmun] (2). His mother was a bond-woman named Marājil al-Bādhghīsiyyah (3). He was born in Rabīʿ al-Awwal of the year 170 AH, on the very night his uncle al-Hādī died and his father Hārūn al-Rashīd assumed the caliphate—an event that took place on a Friday night, as mentioned earlier.

Ibn ʿAsākir (4) said: He narrated hadith from his father, from Hushaym ibn Bashīr, Abū Muʿāwiyah al-Ḍarīr, Yūsuf ibn ʿUṭiyyah, ʿAbbād ibn al-ʿAwwām, Ismāʿīl ibn ʿUlayyah, and Ḥajjāj ibn Muḥammad al-Aʿwar.

Those who reported from him were: Abū Ḥudhayfah Isḥāq ibn Bishr—who was older than he—Chief Judge Yaḥyā ibn Aktham, his son al-Faḍl ibn al-Maʾmun, Muʿammar ibn Shabīb, Judge Abū Yūsuf, Jaʿfar ibn Abī ʿUthmān al-Ṭayālisī, Aḥmad ibn al-Ḥārith al-Shīʿī, al-Yazīdī, ʿAmr ibn Masadah, ʿAbd Allah ibn Ṭāhir ibn al-Ḥusayn, Muḥammad ibn Ibrāhīm al-Sulamī, and Diʿbil ibn ʿAlī al-Khuzāʿī. He (5) also noted that al-Maʾmun travelled to Damascus several times and stayed there for a while.

[Ibn ʿAsākir] (6) further transmitted, through Abū al-Qāsim al-Baghawī, who said, “Aḥmad ibn Ibrāhīm al-Mawṣilī related to us: I heard al-Maʾmun at al-Shammāsiyyah (7) after he had conducted the horse-race (8). He gazed at the great number of people and said to Yaḥyā ibn Aktham, ‘Do you not see?’ He then said: ‘Yūsuf ibn ʿUṭiyyah narrated to us, from Thābit, from Anas, that the Prophet ﷺ said:

‘All creatures are Allah’s dependants, and the most beloved of them to Him (9) are those who are most beneficial to His dependants.’” (10)