The Anaphora of Addai and Mari, named for the two apostles whom tradition credits with evangelising Edessa, is the ordinary eucharistic prayer of the East Syriac Rite, and liturgical scholarship converges on a remarkable judgment about it: in structure and core text it is the oldest anaphora in continuous liturgical use in the world, with many scholars placing its origins as early as the third century in the Aramaic-speaking church of Mesopotamia. Its antiquity shows in its shape.
The prayer addresses much of its course to Christ directly, a primitive trait, and, most famously, it contains no connected narrative of the Last Supper; the words of institution, held in Western sacramental theology to be the essential formula of consecration, are simply not there as a quoted story. For centuries Catholic theology regarded this as a defect that must have been corrected in practice. In 2001 the question was settled the other way: the Pontifical Council for Promoting Christian Unity, with the approval of the Congregation for the Doctrine of the Faith, formally recognised the Anaphora of Addai and Mari as a true and valid eucharistic prayer as the Assyrian Church celebrates it, judging the words of institution present in a dispersed and euchological way rather than as narrative. The ruling, issued to allow shared communion between Chaldean Catholics and Assyrians in need, is one of the most significant liturgical decisions of the modern papacy, an acknowledgment that the ancient East kept a form of the church's central prayer older than the categories later used to judge it.