Muslim martyrdom defies easy categorization. From the genesis of Islam at the time when the first revelations came to the Prophet Muhammad (approx. 610 ce) Muslims have been certain that suffering for the faith constituted a powerful testimonial. Although Muhammad was largely immune to the persecutions described in the Muslim historical texts personally, many of those who first converted to Islam were not. Muhammad preached a radical and exclusive brand of monotheism that was in stark contrast to the fairly easy-going polytheism of the town of Mecca. Mecca had come to some prominence during the century prior to Muhammad's time (born ca. 570) as a result of pilgrimage to the local holy place, the Kaʿba (at that time an unroofed, square building), and some form of trade. Despite this, it was still largely homogeneous in population. Most of the inhabitants were of the tribe of Quraysh, which considered itself to be a merchant aristocracy, with a minority of transients – usually those who were married to Qurashi women or who had taken refuge in the vicinity of the holy place as a result of criminal actions – and a community of slaves.