Relics and Diplomacy between Byzantium and the East Syrian Church: Traces of a Lost Connection in Syriac and Arabic Sources

The Syriac-speaking communities of the Fertile Crescent gradually distanced themselves from the Byzantine world between the 5th and 6th centuries. The East Syrian Church (the Church of the East), in particular, had already marked its separation in 410 (with the Synod of Mar Isḥaq), well before the divisions provoked by the Christological controversies. Nevertheless, this theological wall between Byzantium and the Patriarchate of Seleucia-Ctesiphon did not prevent the circulation of ideas, texts, books, and objects across the Byzantine-Sasanian frontier. Although not abundant in number, several examples preserved in East Syrian hagiography and historiography (composed in Syriac, and from the 9th century onward also in Arabic) bear witness to a fascinating and little-studied case of interreligious and intercultural exchange. One striking example is the translatio of relics and books from the West (the Edessa region) to the East (northern Iraq), attested in the early 7th century in the Book of Governors by Thomas of Marga. During the same period, numerous diplomatic, intellectual, and theological exchanges involved bishops and patriarchs of the Church of the East traveling directly to Byzantium (ca. 550–630). In addition to these material exchanges, there is also evidence of liturgical and hagiographical connections between the Byzantine Chalcedonian world, the West Syrian Miaphysite tradition, and the East Syrian Dyophysite Church. The cult of saints frequently transcended theological and political divisions between churches and empires. For instance, the Vita of John of Daylam, an East Syrian monk and saint of the early 8th century, circulated widely across multiple Christian traditions and survives in several recensions in Syriac, Arabic, Sogdian, and Ethiopic. Even beyond Byzantium, though never entirely detached from it, the Church of the East continued to cultivate certain forms of connection with the Greek West—an aspect of its history that remains to be fully understood and studied.