There is no single leader of Islam, but the prophet of Islam is Muhammad. According to the Qur'an, Muhammad received revelations from Allah about life and piety that he was to spread to the people of the world.
The Qur'an is the Muslim holy book, but Muslims also reference the Old and New Testaments of the Bible. Their prophet was a seventh-century illiterate man who was supposedly chosen to receive the revelation. He was tasked with converting the pagan people in the Arabian peninsula, and later worldwide, into Muslims. Islam is the second-largest world religion at 23.2 percent of the population, following Christianity.