Sunnis say he named no successor; Shi'ites say he picked his son-in-law
[DOC] [TLE] Succession to Muhammad - Wikipedia [PAR] The succession to Muhammad raises questions about the leadership of Islam 
after his death: ... Shias believe that Muhammad named his successor, Ali, at 
Ghadir Khumm; Muslim .... Ali did not change his mind when he pledged 
allegiance to Abu Bakr, Umar and Uthman; ...