In the time of Roman emperor Constantius II (337–361), Bishop Marcus (Mark) of Arethusa was authorized to replace a pagan temple in the city with a Christian church. Under Julian the Apostate (361–363), he was ordered to rebuild the temple. To avoid doing so he fled from the city, but returned to save the Christian people from paying the penalty in his stead, and in 362 underwent very cruel treatment at the hands of the pagan mob, as recounted by Theodoret and Sozomen. He is said to have been the author of the Creed of Sirmium (351) and was counted by Tillemont as an Arian. Research by the Bollandists restored his reputation for orthodoxy. The Roman Martyrology commemorates him on 29 March, with the description: "Saint Mark, Bishop of Arethusa in Syria, who in the time of the Arian controversy held firm to the orthodox faith and was severely maltreated under Julian the Apostate. Saint Gregory of Nazianzus lauds him as an outstanding and saintly old man." The Eastern Orthodox Church celebrates him on 20 March.