One of the oldest extant documents in Islamic history records a set of deeds executed by Muhammad after his migration ( hijra ) in 622 from Mecca to Yathrib, subsequently known as “the City madīna of the Prophet.” Marking the beginning of the Islamic era, the document comprising the deeds has been the subject of well over a century of modern scholarship and is commonly called the “Constitution of Medina”—with some justification, although the first modern scholar who studied it at the end of the 19th century, Julius Wellhausen, more accurately described it as the “municipal charter” ( Gemeindeordnung ) of Medina. In 1889, Wellhausen highlighted the text's antiquity, which has been acknowledged by even the most skeptical of contemporary “source-critical” scholars, Patricia Crone, who thinks that, in Ibn Ishaq's Sira , “it sticks out like a piece of solid rock in an accumulation of rubble.”
Saïd Amir Arjomand (Mon,) studied this question.