This book is concerned with a gospel commentary usually attributed to Ephrem, the great theologian-poet of fourth century Syriac-speaking Christianity. The gospels were known to Ephrem and to his church, primarily, in the form of Tatian's harmony of the gospels or Diatessaron. The focus of this book is that section of Ephrem's Commentary on the Diatessaron which treats the Sermon on the Mount. It also studies Ephrem's portrayal of four gospel characters within his Diatessaron Commentary, and explores the connections between his understanding of the Lord's Sermon teaching and his treatment of these characters. The establishing of such connections highlights the centrality of a number of themes in Ephrem's commentary on the Sermon. The profile of these Sermon themes and of the four gospel characters within Ephrem's writings as a whole is examined.