Sunni Islam is the largest branch of Islam, followed by 85–90% of the world's Muslims, and simultaneously the largest religious denomination in the world. Its name comes from the word Sunnah, referring to the tradition of Muhammad. The differences between Sunni and Shia Muslims arose from a disagreement over the succession to Muhammad and subsequently acquired broader political significance, as well as theological and juridical dimensions. According to Sunni traditions, Muhammad left no successor and the participants of the Saqifah event appointed Abu Bakr as the next-in-line. This contrasts with the Shia view, which holds that Muhammad appointed his son-in-law and cousin Ali ibn Abi Talib as his successor.