As his followers increased, Muhammad became a threat to the local tribes and rulers of the city, whose wealth rested upon the Ka'aba, the focal point of Meccan religious life that Muhammad threatened to overthrow. Tradition records at great length the persecution and ill-treatment towards Muhammad and his followers. Sumayyah bint Khayyat, a slave of a prominent Meccan leader Abu Jahl, is famous as the first martyr of Islam; killed with a spear by her master when she refused to give up her faith. Bilal, another Muslim slave, was tortured by Umayyah ibn Khalaf who placed a heavy rock on his chest to force his conversion.