Followers of a conservative, puritan, orthodox Sunni Muslim movement, Wahhabiya, or Wahhabism, founded in the eighteenth century in Arabia by Muhammad ibn Abd al-Wahhab (1703–1792). After schooling in Iraq and Iran, Wahhab returned to Arabia around 1739, where he began preaching and composed his best known work, Kitab al-Tawhid (Treatise on Divine Unity). Wahhabi was adopted by the Saʿud clan after his marriage to a daughter of Muhammad ibn Saʿud in 1744, and Wahhabi doctrine later became the official state religion of Saudi Arabia. Fiercely opposed to Shiʿism, Wahhabism rejects all rationalist exegesis of the Qurʾan and of the shariʿa. Wahhabis, who are distinguished by their austerity, reject poetry, music, and laughter. Wahhabism has influenced the Muslim Brotherhood and the Salafiyya current. Contemporary radical Islamist movements have also been inspired by Wahhabism, partly through its uncompromising religious ideology and partly through the lavish subventions of the Saudis, who have established madrasas (religious schools) and supported radically conservative social groups all over the Muslim world.