Bp. of Ḥdatta, author of commentaries on both the OT and NT. Little is known of Ishoʿdad’s biography. A native of the city of Maru or Merv, in present-day Turkmenistan, he became bp. of Ḥdatta (al-Ḥadītha), to the southeast of Mosul, ca. 837. In 852, he was a candidate for the patriarchal throne, but he failed to be elected.

Ishoʿdad’s commentaries present the most expansive form of E.-Syr. biblical interpretation. They are preserved in a good number of mss. and they served as sources not only for subsequent E.-Syr. commentators, but also for W.-Syr. authors, such as Dionysios bar Ṣalibi.

Both the theological concepts and the exegetical principles of the commentaries largely reflect the ideas of Theodore of Mopsuestia as they had developed and were transmitted in the later E.-Syr. schools. Works of other authors, however, were also part of the E.-Syr. exegetical tradition, especially those of Ephrem, Basil of Caesarea, the Cappadocians, and John Chrysostom, as well as exegetical writings by various authors of the Schools of Nisibis and Seleucia, among them Narsai, Cath. Mar Aba, and Ḥenana of Adiabene. The use of such a variety of sources sometimes led Ishoʿdad to distance himself from the interpretations of Theodore of Mopsuestia. A notable example is the commentary on the Song of Songs, for which Ishoʿdad juxtaposed the opinion of Theodore, who had expressed reservations as to the inspired character of the biblical book and its usefulness for the Christian reader, and the straightforward allegorical interpretations of authors such as Gregory of Nyssa, John Chrysostom, and others.

Some of the works that Ishoʿdad used had remained outside the scope of interest of his E.-Syr. predecessors. One example is the biblical commentaries of Eusebius of Emesa, excerpts of which Ishoʿdad incorporated in his work. Another example is the Syro-Hexapla, the work of the Syr. Orth. bp. Pawlos of Tella, which was introduced in the Ch. of E. around 800 and from which Ishoʿdad was the first to draw biblical quotations of either the Septuagint or the later Greek versions (Aquila, Symmachus, and Theodotion).