He was born in Mecca, where in c.610 he received the first of a series of revelations, which became the doctrinal and legislative basis of Islam and which were written down c.610–32 as the Koran. His sayings (the Hadith) and the accounts of his daily practice (the Sunna) constitute the other major sources of guidance for most Muslims. In the face of opposition to his preaching he and his small group of supporters were forced to flee to Medina in 622; this flight, known as the Hegira, is of great significance in Islam, and the Islamic calendar (which is based on lunar months) is dated from 622 ad (1 ah). After consolidation of the community in Medina, Muhammad led his followers into a series of battles, which resulted in the capitulation of Mecca in 630. He died two years later, having successfully united tribal factions of the Hejaz region into a force that would expand the frontiers of Islam. He was buried in Medina. Islam is now the professed faith of some 1600 million people.