The Sunnah encompasses reports of the Prophet's statements, acts and approvals. Their legal significance requires attention to transmission and narrator qualification. Mutawatir, mashhur and khabar al-wahid are three central categories.
The book links mutawatir with certain knowledge, mashhur with a level of assurance, and a sound solitary report with an obligation to act under its conditions. A solitary report is neither equivalent to tawatur nor automatically devoid of legal force.