Bp. of Edessa (ca. 684–9, 708) and scholar. Born in the village of ʿEn Deba in the district of Gumya, in the province of Antioch. He entered the monastery of John bar Aphtonia in Qenneshre on the upper Euphrates, where he studied the Scriptures and Greek, and spent some years in Alexandria. The remainder of his life was spent in the region of Syria which was by then under Muslim control. He was ordained by his friend the Patr. Athanasios of Balad and in ca. 684 was appointed bp. of Edessa. However, he resigned after only a few years over what he regarded as a lax attitude to canon law with which he refused to compromise. He made a public demonstration of his position by burning a copy of the canons in front of the residence of the Patr. Yulyanos. He then went to the Monastery of Mor Yaʿqub at Kaysum, near Samosata, and wrote two treatises, one of them against those who broke canon law. Subsequently he was invited to the Monastery of Eusebona to teach the Psalms and the reading of Scripture in Greek: although he was a Syriac-speaker and wrote exclusively in Syriac, Yaʿqub was an enthusiastic proponent of Greek language, literature, and Miaphysite theology. But after eleven years he was forced to leave because of the anti-Greek attitude prevalent in the convent. He moved on to the Monastery of Tell ʿAda along with his disciples and worked on his revision of the Old Testament. In 708 Ḥabbib, who had replaced Yaʿqub as bp. of Edessa, died, and Yaʿqub was recalled to the bishopric. However, he himself died only four months later on 5 June at Tell ʿAda, to which he had returned in order to fetch his library and students. He was buried there, and miracles were said to have been performed at his tomb.

Yaʿqub was a polymath, and although some of his works have failed to survive, many were very influential in the Syr. Orth. Church. His literary works include:

1. A revision and annotation of earlier Syriac translations of the Greek ‘Cathedral Homilies’ and ‘Oktoechos’ of the Miaphysite scholar Severus of Antioch. Completed ca. 701.

2. Yaʿqub’s ‘Hexaemeron’, the first Syriac work to describe the world from the perspective of the biblical creation account. Unfinished at the time of Yaʿqub’s death and completed by his friend Giwargi bp. of the Arab tribes.

3. Many letters on matters ranging from canon law to Bible interpretation. Yaʿqub’s correspondents include Yuḥanon the Stylite of Litarba near Aleppo, Pawlos of Antioch, Eustathios of Dara, Qurisona of Dara, the priest Abrohom, the deacon Gewargis, the sculptor Toma, and Barḥadbshabba.

4. A revision of the Old Testament text, which survives for the Pentateuch, Sam, Is, Dan, and Wisd. It seems to be a hybrid of the Peshitta, Septuagint, and Syro-Hexapla texts, perhaps with the aim of supplementing the Syriac tradition.

5. Commentaries on the Bible, but these only survive as scholia in catenae and ms. collections.

6. Works on canon law, including a treatise on the forbidden degrees of affinity. Yaʿqub’s interpretations are also found in a question and answer series addressed to the priest Addai.

7. A chronicle covering the period from the end of Eusebius of Caesarea’s Ecclesiastical History to his own time (ca. 692). Unfortunately most of this work has perished, but it was used in the 11th cent. by the E. Syr. chronographer Eliya of Nisibis.

8. A handbook of philosophical terms, the ‘Encheiridion’.

9. The first systematic Syriac grammar. It survives only in fragmentary form, but it was an important influence on Bar ʿEbroyo’s grammatical work. In the examples he gave of grammatical rules, Yaʿqub used Greek vowel letters inserted into the consonantal text (similar forms can be found in his Sam ms.), and this method was modified by his successors to become the now familiar W.-Syr. system. Yaʿqub also wrote a letter to Giwargis bp. of Serugh on orthography.

10. Liturgical works: Yaʿqub revised the liturgy of St. James, wrote the ‘Book of Treasures’ which included orders and prayers for baptism, consecration of the waters on the eve of Epiphany, and marriage. He translated the Sedro of Severus for baptism, and composed a horologium with services for the hours of the week, and a calendar of feast days.

11. Several prose homilies: on the Eucharistic sacrifice, unleavened bread, against Dyophysites, and against transgressors of canon law. Two metrical homilies, on the Trinity and Incarnation, and on Faith against the Ch. of E., have been attributed to Yaʿqub, but his authorship of the latter is disputed.