Allaah promised in the Qur’aan that He would take on the responsibility of protecting His final word from loss. He said, “Verily I have revealed the Reminder (Qur’aan), and verily I shall preserve it.” (Soorah al-Hijr (15):9)
Thus, the Qur’aan has been preserved in both the oral as well as written form in a way no other religious book in history has.
Why did Allaah preserve the Qur’aan and allow His earlier books of divine revelation to be changed or lost?
The answer to that question lies in the following three facts:
1. The earlier prophets and their books were sent to a particular people in particular periods of history. Once the period ended, a new prophet was sent with a new book to replace the previous book. So, it was not necessary that these books be preserved by Allaah. The preservation of the earlier books was left up to the people as a test for them. Thus, when the people went astray, they changed what was written in the books which their prophets brought in order to make allowable the things which were forbidden to them. In that way, all of the earlier books of revelation became either changed or lost.
2. Prophet Muhammad (sallallahu ‘alayhi wa sallam) was the last prophet whom Allaah sent, and he was not sent to a particular people or a particular time. He was sent to all of mankind until the end of the world. Allaah said in the Qur’aan,
“I have only sent you (Muhammad) as a giver of glad tidings and a warner to all mankind, but most men do not understand.”
Thus, his book of revelation, the Qur’aan, had to be specially preserved from any form of change or loss so that it would be available to all the generations of man until the last day of the world.
3. The Qur’aan was the main miracle given to Prophet Muhammad (sallallahu ‘alayhi wa sallam) to prove that he was a true prophet of Allaah and not an imposter. So, the Qur’aan had to be saved to prove to the later generations that Muhammad (sallallahu ‘alayhi wa sallam) was really the last prophet of Allaah. All of the false prophets who came after Prophet Muhammad (sallallahu ‘alayhi wa sallam) brought books which they claimed to be revealed from Allaah, but none of them have the miraculous ability to be memorized by thousands, nor have they improved on the message of the Qur’aan. The significance of the Qur’aan’s preservation is that Islaam has been kept in its original purity because of it. Humanity can always return to the sources of Islaam no matter what people may have added or forgotten in time. All of the essential principles of Islaam are to be found in the Qur’aan. Consequently, the preservation of the Qur’aan meant the preservation of Islaam in its final form. The loss of the Gospel of Jesus means that Christians can never return to the true teachings of Prophet Jesus except by accepting Islaam. Similarly, the original Torah was lost when Solomon’s Temple in Jerusalem was destroyed by the Babylonians. Thus, the Jews cannot return to the pure teachings of Prophet Moses except by following Islaam.It is only in Islaam that the pure teachings of the prophets have been preserved without any change. That is why Allaah said in the Qur’aan,
“Verily, the only acceptable religion to Allaah is Islaam.”
 Soorah Saba’ (34):28.
 See The Five Gospels, pp. 2-16.
 See The New Encyclopaedia Britannica, vol. 14, p. 757.
 Soorah Aal ‘Imraan (3):19