According to Bardesanes (ap Euseb. Praepar. Evangel.), there were some Christians in Persia before the end of the second century. In the time of Constantine (see his epistle to Sapor [Euseb.], Vit. l. iv. c. 13) they composed a flourishing church. Consult Beausobre, Hist. Critique du Manicheisme, tom. i. p. 180, and the Bibliotheca Orientalis of Assemani.