According to traditional Islamic beliefs, the Quran was revealed to Muhammad, a trader in the western Arabian city of Mecca founded by the prophet Ismail, which had become a sanctuary for pagan deities and an important trading center. The revelations started one night during the month of Ramadan in 610, when Muhammad, at the age of forty, received the first visit from the angel Gabriel.
The Quran uses the term ummi to describe Muhammad. The majority of Muslim scholars interpret this word as a reference to an illiterate individual, though some modern scholars instead interpret it as a reference to those who belong to a community without a scripture.[6][7]
According to the famous collector of traditions of Muhammad, Muhammad al-Bukhari (who lived about 250 years after Muhammad), Muhammad's wife Khadija bint Khuwaylid described that the first Quranic revelation occurred when the angel Gabriel visited Muhammad and asked him to recite. Muhammad responded ma ana bīqāre'u, which could be translated into a number of ways: 'I do not read' or 'what am I to read/recite?' or 'I will not read/recite'. Gabriel pressed him "until all the strength went out of me; thereupon he released me and said: 'Read!'" This was repeated three times and upon the third, Gabriel released him and said, "Read in the name of the Sustainer who created humankind from a clot! Read! And your Sustainer is the most Beautiful."[8]:39–41 After this Muhammad continued to have revelations sporadically over a period of twenty-three years, until shortly before his death in 11/632.[8]:45
Muslims believe that Gabriel brought the word of God to Muhammad verbatim, and the Quran was divinely protected from any alteration or change. The Quran emphasizes that Muhammad was required only to receive the sacred text and that he had no authority to change it. It is also believed that God did not make himself known through the revelations; it was his will that was revealed.
According to tradition, Muhammad described the experience of revelation:

"Sometimes it is revealed like the ringing of a bell. This form of inspiration is the hardest of them all and then it passes off after I have grasped what is inspired. Sometimes the Angel comes in the form of a man and talks to me and I grasp whatever he says."[8]:43

At times, it was also reported that the experience was painful for Muhammad. For example, he had been heard saying, "Never once did I receive a revelation without thinking that my soul had been torn away from me."[8]:43
After Muhammad would receive revelations, he would later recite it to his companions, who also memorized it or wrote it down. Before the Quran was commonly available in written form, speaking it from memory prevailed as the mode of teaching it to others. The practice of memorizing the whole Quran is still practised among Muslims. Millions of people have memorized the entire Quran in Arabic. This fact, taken in the context of 7th-century Arabia, was not an extraordinary feat. People of that time had a penchant for recited poetry and had developed their skills in memorization to a remarkable degree. Events and competitions that featured the recitation of elaborate poetry were of great interest.
Non-Muslim people questioned the nature and modes of Muhammad's revelations. The Meccans interpreted the Quranic revelations based on their understanding of 'inspiration'. For them, poetry was closely connected to inspiration from a higher spiritual source. For this reason when Muhammad began preaching and reciting the Quran, the Meccans accused him of being a poet or a "poet possessed".
Due to the fact that the Quran was revealed in disjointed verses and chapters, a point came when it needed to be gathered into a coherent whole text. There are disagreements among both Muslim and non-Muslim scholars as to when the Quran was first compiled. A hadith in Sahih al-Bukhari states that the caliph Abu Bakr commanded Zayd ibn Thabit to compile the written Quran, relying upon both textual fragments and the memories of those who had memorized it.[14][15] Some Shia Muslims believe that Ali ibn Abi Talib was the first to compile the Quran into one written text, a task completed shortly after the death of Muhammad.