Ishodad of Merw (9th century), like other East Syrian exegetes, understands himself as an heir of Theodore of Mopsuestia's (died 428) approach to biblical interpretation. The study examines this claim in one of the rare cases where the Syriac translation of Theodore's commentary (on Ps 119 and 139-147) is extant. Ishodad emerges as a competent representative of his scholastic tradition working creatively with his scientific tools. Ishodad's commentary shows traces of Theodore's in less than a third of the verses explained. This reflects the development of medieval academic exegesis and the changed expectations towards biblical interpretation and its presentation. In its highly abbreviated style, Ishodad's commentary shows that it was written for a learned audience for whom one could reduce one's explanations to their essential parts. The study of Ishodad's commentary provides a glimpse into East-Syrian scholarship in Abbasid Mesopotamia as mediating between different exegetical traditions and biblical translations.