As Muslims, we believe that certain Prophets were revealed divine books. For example the Torah, Zabur, Injeel (Gospel) and of course the Quran. All these books taught the belief and worship of One God, but overtime were changed, apart from the Qur’an, in which Allah promises to protect as his final revelation.

The Quran, the last revealed word of God, is the primary source of every Muslim’s faith and practice. It deals with all the subjects which concern human beings: wisdom, doctrine, worship, transactions, law, etc., but its basic theme is the relationship between God and His creatures. At the same time, it provides guidelines and detailed teachings for a just society, proper human conduct, and an equitable economic system.

The Qur’an is for all people, from all walks of life, it was sent to the entirety of mankind.

The Qur’an has never ever been changed since the moment it was brought down, studies have concluded these findings, and it is a true testament to the verse reveled in Qur’an

“Indeed, it is We who sent down the Qur’an and indeed, We will be its guardian.” (Qur’an 15:9)

Allay says in the Quran: “Then do they not reflect upon the Qur’an? If it had been from [any] other than Allah, they would have found within it much contradiction.” (Qur’an 4:82)

Allah says in the Quran, if you want to contest it, come up with just “One Chapter” of it’s like, but you will not be able to.

Say, “If mankind and the jinn gathered in order to produce the like of this Qur’an, they could not produce the like of it, even if they were to each other assistants.” (Qur’an 17:88)

“And if you are in doubt about what We have sent down upon Our Servant [Prophet Muhammad ], then produce a surah the like thereof and call upon your witnesses other than Allah , if you should be truthful.” (Qur’an 2:23)

“O mankind, there has come to you a conclusive proof from your Lord, and We have sent down to you a clear light. So those who believe in Allah and hold fast to Him – He will admit them to mercy from Himself and bounty and guide them to Himself on a straight path.” (Qur’an 4:174-175)

Refer: http://www.islam-guide.com/frm-ch3-1.htm

Refer: http://invitetoislam.org/quran/