Venerable white-bearded dervishes and high-heeled girls with garish lipstick found rare common ground before dawn on Tuesday, celebrating an Iranian holiday with the mystical chants of the Sufis. Sufi Muslim spirituality is largely tolerated under Iran’s strict Islamic laws, although senior religious figures occasionally call for a clampdown on its rites. Under an almost full moon, several hundred Iranians came to celebrate the birthday of the ‘Mahdi’ at the Zahir-od-dowleh cemetery in northern Tehran, a dervish hub where many writers and artists are buried. The Mahdi is a key figure of Shi’ite Islam, a descendant of the Prophet Mohammad whose...