The Quran is a book of revelations from God. Today it exists in the form of a book consisting of 114 chapters. They were sent down by the angel Gabriel or Jibril, bit by bit according to the demand of circumstances. The Quran is a revealed book: it is not authored by a human being. It is the actual word of God in human language. The Quran began to be revealed to the Prophet Muhammad PBUH through the angel Gabriel, in A.D. 610, while the Prophet was sitting in seclusion in the cave of Hira at the top of the Mountain of Light, two miles from Makkah. Thus the scriptures were not revealed in book-form at one point of time. Their various parts were revealed as the occasion demanded. It was later compiled in Madinah during the last days of the Prophet pbuh. The entire revelation was completed over a period of 23 years. The last passage was revealed to the Prophet pbuh while he was addressing a gathering at Mount Arafat after performing his last Hajj in A.D. 622.