'Kitab at-Tabaqat al-Kabir' by Abu 'Abdullah Muhammad ibn Sa'd is one of the most important and earliest surviving collections of biographical details of the early Muslims, spanning just over the first two centuries of Islam. It is a rich storehouse of information compiled from all the sources available to Ibn Sa'd, as a result of which, the reader is given a vivid insight into the lives of the early Muslims and how extraordinary they were.