Narrated Aisha (the wife of the Prophet):
The commencement (of the Divine Inspiration) to Allah's Apostle was in the form of true dreams in his sleep, for he never had a dream but it turned out to be true and clear as the bright daylight. Then he began to like seclusions, so he used to go in seclusion in the cave of Hira where he used to worship Allah continuously for many nights before going back to his family to take the necessary provision (of food) for the stay. He come back to (his wife) Khadija again to take his provision (of food) likewise, till one day he received the Guidance while he was in the cave of Hira. An Angel came to him and asked him to read. Allah's Apostle replied, "I do not know how to read." The Prophet added, "Then the Angel held me (forcibly) and pressed me so hard that I felt distressed. Then he released me and again asked me to read, and I replied, 'I do not know how to read.' Thereupon he held me again and pressed me for the second time till I felt distressed. He then released me and asked me to read, but again I replied. 'I do not know how to read.' Thereupon he held me for the third time and pressed me till I got distressed, and then he released me and said, 'Read, in the Name of your Lord Who has created (all that exists), has created man out of a clot, Read! And your Lord is the Most Generous. Who has taught (the writing) by the pen, has taught man that which he knew not." (96.1-5). Then Allah's Apostle returned with that experience;
and the muscles between his neck and shoulders were trembling till he came upon Khadija (his wife) and said, "Cover me!" They covered him, and when the state of fear was over, he said to Khadija, "O Khadija! What is wrong with me? I was afraid that something bad might happen to me." Then he told her the story. Khadija said, "Nay! But receive the good tidings! By Allah, Allah will never disgrace you, for by Allah, you keep good relations with your Kith and kin, speak the truth, help the poor and the destitute, entertain your guests generously and assist those who are stricken with calamities." Khadija then took him to Waraqa bin Naufil, the son of Khadija's paternal uncle. Waraqa had been converted to Christianity in the Pre-lslamic Period and used to write Arabic and write of the Gospel in Arabic as much as Allah wished him to write. He was an old man and had lost his eyesight. Khadija said (to Waraqa), "O my cousin! Listen to what your nephew is going to say." Waraqa said, "O my nephew! What have you seen?" The Prophet then described whatever he had seen. Waraqa said, "This is the same Angel (Gabriel) who was sent to Moses. I wish I were young." He added some other statement. Allah's Apostle asked, "Will these people drive me out?" Waraqa said, "Yes, for nobody brought the like of what you have brought, but was treated with hostility. If I were to remain alive till your day (when you start preaching). then I would support you strongly." But a short while later Waraqa died and the Divine Inspiration was paused (stopped) for a while so that Allah's Apostle was very much grieved. Narrated Jabir bin 'Abdullah: While Allah's Apostle was talking about the period of pause in revelation. he said in his narration. "Once while I was walking, all of a sudden I heard a voice from the sky. I looked up and saw to my surprise, the same Angel as had visited me in the cave of Hira.' He was sitting on a chair between the sky and the earth. I got afraid of him and came back home and said, Wrap me! Wrap me!" So they covered him and then Allah revealed: 'O you, wrapped up! Arise and warn and your Lord magnify, and your garments purify and dessert the idols.' (74.1-5) Abu Salama said, "(Rijz) are the idols which the people of the Pre-lslamic period used to worship." After this the revelation started coming frequently and regularly.
Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 478
Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 478