Probably (as Duval suggests) the use of Syriac in these regions went hand in hand with the spread of the monophysite doctrine, for the liturgies and formulas of the Jacobite Church were composed in Syriac. Similarly the spread of Nestorian doctrines throughout the western and southwestern regions of the Persian Empire was accompanied by the ecclesiastical use of a form of Syriac which differed very slightly indeed from that employed farther west by the Jacobites.
Bedjan, p. 115; cited by Duval, Litt.
Duval, op. cit.
Tixeront, Origines de l'Eglise d'Edesse, p. 93, and Duval, op. cit.