In her book The Formation of Christendom, Judith Herrin writes:
It was in their role as intercessors between man and God that the icons commanded particular devotion. Numerous legends of women, whose inability to conceive a child (or sometimes, more particularly, a son) was removed by prayers directed to icons, reflect an anxiety common to many medieval societies. St. Glykeria, the patron of Herakleia, promised a child to the parents of St. Elizabeth through the medium of her icon; Elizabeth was in due course dedicated to here in front of the same image. Similarly, a childless couple was blessed by the Virgin’s icon at Sozopolis, and the mother of St. Stephen had her longing for a son satisfied at the Blachernae shrine in Constantinople. For the cure of disease rather than infertility, the medical saints, Cosmas and Damian, Artemios, Gebronia, and others, were frequently invoked and their icons consulted. Incubation for one or more nights in their shrines—the pagan custom of sleeping close to the god—was rewarded by nocturnal visits of the saints (again, recognisable in features familiar from their images) and finally by cures. The oil burning in lamps suspended in front of icons also had curative power, as did the miraculous effluents that emerged from the Sozopolis icon or the relics of St. Euphemia in Chalcedon. Icons were also appreciated for their power to move: in the early seventh century, Patriarch Sophronios wrote down the ancient legend of St. Mary the Egyptian, who was allegedly converted by a picture of the Virgin preserved at Jerusalem in his time.