First, there are Allah's rules which we've talked about in Pain, Pleasure and Prejudice, and then there are the hadiths (or hadith, in English academic usage hadith is often both singular and plural), the sayings and example i.e. deeds of the Prophet Muhammad.
The authenticated sayings and example of the Prophet Muhammad, along with Koran, are the basis of Sharia law.
Given the fact that [hadiths are] often used as the lens through which to interpret the Koran, many Muslim jurists consider [them] to be even a greater authority on the practice of Islam.
Sam Harris, The End of Faith - Religion, Terror and the Future of Reason, 2004, W. W. Norton & Company.
Get to know the real Muhammad as his closest friends and his child-bride Aisha recall what he said and did during the period of his Call.