Muhammad's migration to Medina. Prior to these revelations, Muhammad and the Muslims in Medina had prayed towards Jerusalem as the qibla, the same direction as the prayer direction—the mizrah—used by the Jews of Medina. Islamic tradition says that these verses were revealed during a prayer congregation; Muhammad and his followers immediately changed their direction from Jerusalem to Mecca in the middle of the prayer ritual. The location of this event became the Masjid al-Qiblatayn ("The Mosque of the Two Qiblas"). There are different reports of the qibla direction when Muhammad was in Mecca (before his migration to Medina). According to a report cited by historian al-Tabari and exegete (textual interpreter) al-Baydawi, Muhammad prayed towards the Kaaba. Another report, cited by al-Baladhuri and also by al-Tabari, says that Muhammad prayed towards Jerusalem while in Mecca. Another report, mentioned in Ibn Hisham's biography of Muhammad, says that Muhammad prayed in such a way as to face the Kaaba and Jerusalem simultaneously. Today Muslims of all branches, including the Sunni and the Shia, all pray towards the Kaaba. Historically, one major exception was the Qarmatians, a now-defunct syncretic Shia sect which rejected the Kaaba as the qibla; in 930, they sacked Mecca and for a time took the Kaaba's Black Stone to their centre of power in Al-Ahsa, with the intention of starting a new era in Islam. Religious significance Etymologically, the Arabic word qibla () means "direction". In Islamic ritual and law, it refers to a special direction faced by Muslims during prayers and other religious contexts. Islamic religious scholars agree that facing the qibla is a necessary condition for the validity of salah—the Islamic ritual prayer—in normal conditions; exceptions include prayers during a state of fear or war, as well as non-obligatory prayers during travel. The (Muhammad's tradition) also prescribes that Muslims face the qibla when entering the ihram (sacred state for hajj), after the middle (stone-throwing ritual) during the pilgrimage. Islamic etiquette (adab) calls for Muslims to turn the head of an animal when it is slaughtered, and the faces of the dead when they are buried, toward the qibla. The qibla is the preferred direction when making a supplication and is to be avoided when defecating, urinating, and spitting. Inside a mosque, the qibla is usually indicated by a mihrab, a niche in its qibla-facing wall. In a congregational prayer, the imam stands in it or close to it,