Muhammad received revelations from Gabriel, which constitute the Koran, Islam's holy book. He initially confided these only in his wife and close circle, beginning public preaching over two years later. Historians like Vernon O. Egger describe Islam as a 'religio-social reform movement,' led by Muhammad, who grew up an impoverished orphan. Mecca at that time featured the pagan Kaaba shrine and pagan idols, while also serving as a trade hub with significant wealth inequality between a rich elite and poor families. Muhammad called on Arabians to share wealth and create a society protecting the weak.