The Commentary of Theodore of Mopsuestia on the Lord’s Prayer and on the Sacraments of Baptism and the Eucharist is an important witness to the development of Christianity. Theodore (c. 350-428) was clearly the most important biblical scholar of his age. In a series of six homilies Theodore here addresses the Lord’s Prayer as a springboard to discuss what actually constitutes prayer. His homilies on the sacraments are essential witnesses to the historical development of these sacraments. His work here is basically a commentary on the text of the liturgy, an awareness of the centrality of the sacraments to the life of the church in his age.