Muslims believe that the Quran is a complete record of the exact words revealed by God through the Archangel Gabriel to the Prophet Muhammad (may God bless him and grant him peace). It was memorized in its entirety by many of his followers, and throughout his prophetic mission it was continuously dictated to his companions and was written down by scribes who also cross-checked it during his very lifetime. Not one word of its 114 surahs (chapters) has been changed over the centuries. In summary, the Quran is in every detail the same unique and miraculous text that was revealed to the Prophet Muhammad (peace be upon him) over fourteen centuries ago.
The Quran is the principle source of every Muslim’s faith and practice. It deals with everything that may be of concern to the human being, including profound spiritual wisdom; religious doctrine and ethics; and worship and law; but its basic theme is the intimate relationship between God and His creatures and the lessons that can be learned from this relationship throughout history. At the same time, the Quran provides guidelines for a just and good society, proper human conduct, and equitable economic practices.
He (God) has sent down to you the Book (the Quran) with truth, confirming what was revealed aforetime; and He sent down the Torah (of Moses) and the Gospel (of Jesus) before this as a guide to humankind; and He sent down the Criterion (the Quran). (Quran 3:3-4)