The geography and cultural influences in Arabia during the 6th century a.d. had a significant influence on the beginning and development of the religion of Islam. Muhammad's early life was normal. When he was 40, he claimed to have a revelation from the angel Gabriel about worshiping the one "true" God, Allah. He receives further revelations that he records in what has become known as the Quran. Because of his revelation, Muhammad destroyed the family idols and then fled to Medina with a group of his supporters. There were significant military battles in which Muhammad and his followers defended themselves even though they were greatly outnumbered. Some of the Muslim mosques that were built have great religious and historical significance.