Qur'an - The only divine scripture that has remained in the world completely intact up to the present day is the Qur’an. It is God's ultimate and final message to mankind and the primary source of Islamic doctrine. It contains information and legislation which encompasses all spheres of human life.
There is only one version of the Qur’an, and unlike previous scriptures, it remains unaltered in its original Arabic text. Initially, the revealed words were memorized by a large number of those who heard them directly from the Prophet. In addition, the entire revelation was recorded by several scribes during his lifetime, and its verses placed in the order he designated. Within a year after the Prophet's death, the written portions were collected and carefully checked against what had been memorized by his companions. Only that which was corroborated and witnessed was approved. The verified documents were then bound together, and from that volume a standard copy was later inscribed, rechecked, endorsed, reproduced and distributed - all within less than 25 years of the Prophet's demise. The Qur'an has been copied, printed, read, recited and memorized by millions of Muslims throughout the world up to the present day, and scholars have confirmed without a doubt that not the slightest change in content has occurred during its transmission from one generation to another.
The Qur'an states that this universe was not formed by chance, nor is it left to chance. God created it for a purpose and subjected it to physical laws for a specific period of time. Man was created for a purpose as well - to serve God upon the earth and live according to His law, which means the establishment of justice and attainment of practical solutions for human problems. The Qur'an does not condemn any religion directly; rather, it acknowledges the good works of previous religious communities but faults them for departing from the teachings of their prophets. It urges every religious person to search for the truth, to purify his belief, obey his Creator and adhere to righteous conduct. It states that there is an ultimate consequence for every action, good and evil, and that there is a greater life following the present one in which complete justice will be realized for every human being, in fact, for every creature that ever existed.
The Qur'an is basically a book of guidance but it does contain some amazing scientific facts. They are amazing because although they were revealed to Prophet Muhammad over 14 centuries ago, they were not really understood by man until scientists "discovered" them in recent times. In addition to religious and moral guidance it contains numerous verses that speak of the universe, its components and phenomena - the earth, sun, moon, stars, mountains, wind, rivers and seas, plants, animals, and successive stages of development of the human being. It appeals to logic, following clear reasoning and citing evidences from the created universe, from history and from the human soul to establish not only the existence of God, but also His uniqueness and absolute perfection.
Muhammad and the Qur'an - Opponents of Islam sometimes allege that Muhammad himself wrote the Qur’an or that he copied or adapted it from previous scriptures. But it is known that the Prophet's contacts with Jews and Christians was negligible before his emigration from Makkah, and after it, his role was that of a teacher, openly inviting the Jews and Christians to accept Islam while pointing out how they had deviated from the true monotheism taught by their prophets.
Historically and logically, it cannot be established that there was any human source for the Qur’an or that the Messenger of Allah learned it from the Jews or Christians. His enemies kept a close watch on him hoping to find confirmation of their claim that he was a liar. But they could not point to a single instance when the Prophet might have had secret meetings with people of other faiths.
At the time the Qur'an was revealed, his contemporaries among the Arabs who were known for linguistic eloquence acknowledged that its language was unique and distinctly different from the speech of Muhammad, a man well known to them. The Qur'an states that the Prophet was an unlettered man, so if that had not been true his opponents would surely have exposed him. There is, however, not a single report to this effect, and no one denied his illiteracy. At the same time, no one denied that the Qur'an was unequaled in eloquence, impact and clarity, including those who rejected its message.
It was a sign of Muhammad's prophethood that he was an illiterate man. He had to be, so that he could never be accused of composing or editing the divine revelations. This fact also eliminates suspicion that he had learned what he preached from earlier scriptures. The information he passed to his people was not obtained through reading and research; it was a kind of knowledge that could only have come from the Creator of the universe.
It is not difficult to verify that Muhammad did not possess knowledge of many things mentioned in the Qur'an, such as historical events, natural phenomena and future occurrences. The Qur'an even states in several places that Muhammad and his people did not know these facts, so again, had it been otherwise, his adversaries would have capitalized on that claim to discredit him. Only recently, within the last two centuries, have advancements in research technology led to the discovery of facts that had been mentioned in the Qur'an by the unlettered prophet over fourteen centuries ago. Among them are these few examples:
The creation of the universe from a single entity and of life from water: Have those who disbelieved not considered that the heavens and the earth were a joined entity, and We separated them and made from water every living thing?
All creation is based on duality, made up of pairs, counterparts or opposites: And of all things We created two mates.
The different natures of the sun and moon: It is He [the Creator] who made the sun a shining light and the moon a derived light and determined for it phases – that you may know the number of years and account [of time].
The rotation of the earth: He created the heavens and earth in truth. He wraps the night over the day and wraps the day over the night.
The expansion of the universe: And the heaven We constructed with strength, and indeed, We are [its] expander.
The sun is not stationary but moves in a specific direction for a limited term: And the sun runs [on course] toward its stopping point.
These are words that were recited by Muhammad, the unlettered prophet. Nothing mentioned in the Qur'an contradicts any established scientific fact, and it addresses these facts with the precision of a scientist. Could the most highly literate, well read or scholarly man of that period, or even of the centuries that followed, possibly have come up with anything remotely similar? The answer is obvious.
Although not meant to be a book of scientific facts as such, the Qur'an mentions certain realities that would only be recognized and appreciated by men in later centuries - as undeniable evidence that it was not the work of Muhammad or of any man, but divine revelation from the Creator of these phenomena. Being the final revelation to mankind, God made the Qur'an a continuing miracle containing evidences to be uncovered gradually as men increase in knowledge of their universe.
Hadith - The teachings of Prophet Muhammad, apart from the text of the Qur'an, are also available today and contained in verified records. His sayings, actions and reactions in every situation throughout his life were related and recorded by those who actually witnessed or heard them. A narration of this kind is called a hadith. Every hadith has two parts: the text and the list of transmitters. Even when the text seems correct and logical, it must be supported by an unbroken chain of reliable reporters going back directly to the Prophet himself in order to be accepted by jurists. Scholars carefully scrutinize the reliability of the transmitters, accepting only those hadiths whose chain of narrators is known to be completely reliable and sound. When verified as authentic, these narrations become a supplement to the Qur'an as the basic foundation of Islamic legislation.
The science of hadith criticism began at an early date. The Prophet's companions learned and passed on his teachings by three methods: memorization, written records and practice. They not only memorized and recorded the revelations which made up the Qur'an, but also committed to memory the exact words used by the Prophet in his own statements as well as descriptions of his behavior and character. After his death, as Islam was spread by the companions into Asia and North Africa, this knowledge accompanied them, and their students faithfully preserved it for following generations.
As the narrations were subsequently conveyed from teacher to student, it is a credit to their scholarship that the narrations were always preceded by a list of narrators going back to the Prophet himself. This enabled later scholars to check out each narration and reject it if the chain of narrators contained anyone who was unknown or was known to be weak in memory or prone to error. Only those narrations whose chains were complete and whose transmitters were unblemished could actually be attributed to the Prophet and accepted as authoritative.
This kind of scholarship became all the more essential in later years when some Muslims began to forge hadiths to support their own views and spread them among the common people. Although they succeeded in their deception for a time, the false narrations were eventually exposed by hadith specialists. Their strict and precise methodology enables us today to know which hadiths are authentic and which ones are weak and unacceptable as evidence. The great body of information so conscientiously collected and thoroughly analyzed for accuracy by Muslim scholars now fills hundreds of volumes, not to mention the studies which have developed around it.
 Meaning literally: a "recitation" or "reading".
 Thus, it is easily accessible for study, as Arabic is a language used and understood by millions of people in the world today.
 It is true that there are some similarities between the Qur’an and the Bible, but this does not indicate that later prophets plagiarized from former ones. It merely points to the common source, which is the Creator of mankind, and to the continuance of His basic message of monotheism. Moreover, there was no Arabic version of the Bible in existence at the time of Prophet Muhammad. The earliest Arabic version of the Old Testament is that of R. Saadias Gaon of 900 CE - more than 250 years after the death of Prophet Muhammad. And the oldest Arabic version of the New Testament was published by Erpenius in 1616 CE - about 1000 years after his death.
 In addition, the Qur'an, on occasion, reproaches the Prophet and brings his attention to some unintentional errors. It is quite unlikely that he would have included such criticisms of himself had he been its author.
 Qur'an - 21:30.
 Qur'an - 51:49. In contrast, the Creator is one, with no counterpart and nothing resembling Him in any way.
 Qur'an - 10:5. Other verses (25:61 and 71:16) refer to the sun as a burning lamp.
 Qur'an - 39:5. The alternate "wrapping" of sunlight and darkness is caused by the earth's turning in one direction.
 Qur'an - 51:47. The Creator refers to Himself in the plural form which denotes power, grandeur and majesty.
 Qur'an - 36:38. The sun, as a tiny member of this vast universe is progressing within it toward a final destination, which indicates an end to the present creation.