Hal where do the two main divisions of muslims come from?

At the death of prophet Muhammad, two denominations emerged over a disagreement as to who should become the successor of Muhammad since he did not appoint anyone.

The majority, called the Sunni, chose Abu Bark, Muhammad's father-in-law, as caliph. A minority opposing this election, the Shia, chose Ali ibn Abi Tabib, Muhammad's son-in-law and cousin as Muhammad's successor. Ever since, the differences between the two major trends of Muslim have kept them opposed to each other,

must repent and believe in god.

or the book

journey across time - chapter 10 "the rise of christianity"