The Arabic treatise edited and translated here was written in the middle of the 9th century CE by ʿAlī ibn Sahl Rabban aṭ-Ṭabarī, a Christian convert to Islam and one of the most remarkable thinkers of his time. The text can be described as a manual towards the preservation of health, addressed directly to the ʿAbbāsid caliph al-Mutawakkil and his household. It represents not only the oldest extant specimen of its kind, but is also distinguished by its largely non-technical language, as well as by a narrative style that creates an unusual interface with classical Arabic prose literature. The Greek and Indian sources upon which aṭ-Ṭabarī relied testify to the synthetic and inclusive character of early Islamic medicine.