In this section located in the inner surface of the outside wall of the church, the return of the holy family from Egypt is taken up as subject-matter. An angel comes up to Joseph one day during his sleep, and tells him to go to Egypt, taking with him Mary and Jesus, and stay there until the time of return is made known to him. This must be done, because soon King Herod will start a search for the innocent Jesus to have him killed. Upon this warning Joseph flees to Egypt, taking with him Mary and Jesus. On this panel, the town of Nazareth is seen on the right. On the left, Joseph is seen asleep on a mattress. An angel comes up to the sleeping Joseph and tells him that since King Herod is dead, they may go back to Nazareth. (Matthew 2: 12-22}. In the middle a horse is seen ready, together with Mary and Joseph holding Jesus on his shoulders. On the vault (flying buttress), the icons of such saints as Philemon, Calinikus, Tirsus and Apolinus are presented.
Above text and pictures are from the book titled "Chora Byzantium's Shining Piece of Art".
You can purchase "Chora Byzantium's Shining Piece of Art" book and other Turkey related books from Explore Turkey Bookstore.