Teacher of biblical interpretation, author, cath. (540–52). Born from Zoroastrian parents, Aba converted to Christianity and studied at the School of Nisibis. He traveled to the Roman Empire and visited Edessa (where he was taught Greek, probably by his later disciple Toma of Edessa), Palestine, Egypt, and Constantinople. Upon his return, he became a teacher of biblical interpretation (mpaššqānā) at the School of Nisibis and subsequently at the School of Seleucia-Ctesiphon, which he is said to have founded. Following the death of Cath. Pawlos, he was elected as his successor in 540. In 544 an itinerant synod was held, during which Aba, accompanied by a changing number of bishops, visited several dioceses, many of which still suffered from the division in the church that had existed prior to the short tenure of Cath. Pawlos. The Synodicon Orientale has preserved the following documents, which are related to this ecclesiastical visitation and, more broadly, to Aba’s reforms: 1. on reform of church governance; 2. on the orthodox faith; 3. on the politeia of correct behavior (focusing on Christian marriage and rejecting various kinds of illicit unions); 4. on the deposal of the initiators of division and schism; 5. on the various degrees in the ecclesiastical hierarchy; 6. a letter entitled Practica (fragments); 7. canons (1–40; incomplete). Aba came into conflict with the Persian authorities and spent several of his years as cath. in prison and in exile.

The sources attribute to Aba several commentaries on OT and NT books, of which only fragments exist in later works, such as the commentaries of Ishoʿdad of Merv. During his travels, around 530, he served as the instructor in biblical matters to the Egyptian author Cosmas Indicopleustes, who ca.  550 wrote his ‘Christian Topography’. Cosmas (in Book II.2) acknowledges Aba, whom he calls Patrikios (derived from the Greek word for ‘father’), as his source and is aware of Aba’s later election as cath. in Persia. Interested in the Greek originals of Theodore of Mopsuestia’s and Nestorius’s works, Aba may have gathered around him a team of translators. One of these may have been the Syriac translator of Nestorius’s ‘Book of Heraclides’, who dedicated his work to Aba. A comment in the Chronicle of Siirt led Baumstark to suggest that Aba may have authored a Syriac translation of the Greek OT, but this cannot be substantiated.

In addition to a number of Syriac and Arabic sources providing details of Aba’s life, there is an important Syriac Life (published by Bedjan), which presents itself as the work of one of Aba’s disciples. Two of Aba’s other disciples, Qiyore of Edessa and Toma of Edessa (who died in Constantinople around 543), are known through their own writings.