Theodoros the Great Ascetic
Our father among the saints Theodoros the Great Ascetic (also known as Theodore of Edessa) was a monk of the monastery of St. Savas near Jerusalem who became bishop of Edessa in Syria. His feast day is celebrated on July 9 or July 19. His Life was written by Basil of Emesa. The work A Century of Spiritual Texts is included in the Philokalia and is believed to have been written by St. Theodoros.
In the middle of the 9th century, St. Theodore of Edessa converted the "Saracen king," Muawid, one of the three sons of the Umayyad caliph Mutawakkil (847-861 A.D.), to Orthodoxy, baptizing him with the name John together with his three confidants. 
- The Philokalia, v. 2.