The Báb wrote hundreds of letters and books teaching who he was and what the rules of his religion were. The Báb's new rules replaced the "Sharia law" or Muslim rules for his followers. Bábism became very large; over ten thousand people believed in the Báb. The Shi'a clergy, or leaders of Islam in Iran hated the Báb and tried to harm people who followed his religion. In 1850 a firing squad shot the Báb in Tabríz, Iran.