Reliquary Box with Scenes from the Life of John the Baptist. Byzantine, 14th century.
Source: The Cleveland Museum of Art, via Treasures of Heaven:
The Christian cult of John the Baptist emerged early as a result of his prominence in the account of the Gospels, which credit him as the first to recognize Christ as the promised Savior. After his execution at the fortress of Machaerus, his remains were allegedly moved to Sebaste. Despite reports that John’s coffin “was opened, his bones burned, and his ashes scattered” during the reign of Julian the Apostate (Theodoret, Ecclesiastical History 3.3), Christian pilgrims such as Egeria in the 380s continued to visit his tomb. His head, however, was taken to the capital, where it was solemnly deposited on 18 February 391 in a church, richly endowed by Emperor Theodosius I. Over the centuries, at least thirty-six churches were dedicated to St. John the Baptist in Constantinople alone, attesting to his exceptional status among the saints and martyrs venerated in the Byzantine Empire.
The painted wood box likely served as a container for one of the saint’s relics. Several such relics—two fragments of his skull, his right arm, and locks of his blood-clotted hair—were kept and venerated in churches and monasteries at Constantinople into the late Byzantine period.