The Qur'an is the final revelation from God to mankind, revealed to the Prophet Muhammad over 23 years. It is comprised of 114 chapters of varying lengths, divided into verses. Some chapters were revealed in Mecca focusing on beliefs like tawhid (the oneness of God), while others revealed in Medina provided legislative rulings. The Qur'an remains completely preserved in its original Arabic language, having been memorized and written down during the Prophet's life. It is the principal source of Islamic teachings and considered the literal word of God by Muslims.