Article révisé par les pairs
Résumé : This short article suggests revising the datation of the Coptic codex Pierpont Morgan Inv. M 636, on the basis of a close analysis of a fragmentary Arabic protocol, kept on five of its leaves and paleographically dating from the beginning of the Abassid era. Such a document being considered a "fiscal stamp", it has to contain, among other the name of the caliph and the governor of Egypt under whom the papyrus roll was manufactured. In this case, those names are lost but we still have the mention that the governor was the son of an "amîr almu'uminîn", i.e. a caliph. Luckily enough, only one governor of Abbassid Egypt was the son of a caliph, Ubayd Allah, whose father was the caliph Al-Mahdi and who served as governor of Egypt under the Caliph Harûn al-Rashîd in 795-797. These observations allow to suggest the end of the eight century as a new datation for the production of the papyrus roll, which is thus fifty years older than what was previously thought.