The Monastery of Tell ʿAda, also known as the ‘Great Monastery’, is located just over 48 km. from Aleppo; 1500 m. north of the present village of Tell ʿAda. At its apogee (5th–9th cent.) Tell ʿAda was a vibrant center for W.-Syr. monasticism. Tell ʿAda is thought to have been founded by the monk Ammianos and his disciple Eusebios in the mid-4th cent. Monks from Tell ʿAda were instrumental in the founding of other Syr. Orth. monasteries, such as the neighboring Monastery of Eusebona. Tell ʿAda occupied a prominent place in the Syr. Orth. Church from its founding through the 10th cent., after which little else is known.

The 5th-cent. writer Theodoret of Cyrrhus appears to have spent some time in this monastery. In his ‘History of the Monks of Syria’ (ch. 4) he describes a large community of monks at Tell ʿAda, a community that was already spreading out to found other monasteries. One surviving 6th-cent. ms., written in this monastery’s scriptorium, contains a collection of poetry from Isḥaq of Antioch. Some letters to Tell ʿAda also survive. The 6th-cent. Syr. Orth. bp. Philoxenos of Mabbug addressed a well-known letter to the monks of Tell ʿAda (ed. Guidi 1884). Another letter purporting to be from Basil the Cappadocian appears in an early 6th-cent. ms. (ed. Albert).

Tell ʿAda is famous as the last residence of Yaʿqub of Edessa and the place where he undertook his revision of the Old Testament. According to Michael Rabo, Yaʿqub resided here during the last nine years of his life before he was asked to return to his bishopric. After living in Edessa for four months, Yaʿqub traveled to Tell ʿAda in order to retrieve his books. It was there that illness overcame Yaʿqub and he died on 5 June 708. A marginal note by Yaʿqub in his revision of the Cathedral Homilies of Severus discloses his familiarity with the region of Tell ʿAda and the neighboring Monastery of Mar Eusebona (Hom. 30, PO 36.4, 617).

The ruins of Tell ʿAda have been dated by Tchalenko to the 5th cent., although it is recognized that the foundation of this monastery may date back to the mid-4th cent. A number of Syriac inscriptions from Tell ʿAda still exist. One of the later inscriptions, dated 941/2, refers to patr. Yoḥannan V bar Abgare.