Answer
Mehmed IV was the Ottoman Sultan during Sabbatai Zevi's imprisonment. Zevi was a Jewish mystic who proclaimed himself the Messiah in the mid-17th century. His teachings and actions caused great controversy within the Jewish community and attracted the attention of the Ottoman authorities. Mehmed IV ordered Zevi's arrest and imprisonment in 1666. Zevi was held in various prisons in the Ottoman Empire until his death in 1676.