At the age of 40, while engaged in a meditative retreat, Muhammad received his first revelation from God through the Angel Gabriel.

This revelation, which continued for twenty-three years, is known as the Qur'an.

Soon after Muhammad began to preach the message he heard from Gabriel, he and his small group of followers suffered bitter persecution which grew so fierce that some of them were forced to flee to Abyssinia where they were treated well by the Christian ruler.

In the year 622 the remaining Muslims were instructed to migrate to Madinah, some 260 miles to the north of Makkah. This event, the Hijra, (migration) marks the beginning of the Muslim calendar.

After several years, the Prophet and his followers were able to return to Makkah, where they forgave their enemies and established Islam definitively.

Before the Prophet died at the age of 63, the greater part of Arabia was Muslim, and within a century of his death Islam had spread to Spain in the West and as far East as China.