Narrated Yahya bin Abi Kathir:

I asked Aba Salama bin `Abdur-Rahman about the first Sura revealed of the Qur'an. He replied "O you, wrapped-up (i.e. Al Muddaththir)." I said, "They say it was, 'Read, in the Name of your Lord Who created,' (i.e. Surat Al-`Alaq (the Clot)." On that, Abu Salama said, "I asked Jabir bin `Abdullah about that, saying the same as you have said, whereupon he said, 'I will not tell you except what Allah's Messenger (ﷺ) had told us. Allah's Messenger (ﷺ) said, "I was in seclusion in the cave of Hiram', and after I completed the limited period of my seclusion. I came down (from the cave) and heard a voice calling me. I looked to my right, but saw nothing. Then I looked up and saw something. So I went to Khadija (the Prophet's wife) and told her to wrap me up and pour cold water on me. So they wrapped me up and poured cold water on me." Then, 'O you, (Muhammad) wrapped up! Arise and warn,' (Surat Al Muddaththir) was revealed." (74.1)

Narrated Yahya:

I asked Aba Salama, "Which Sura of the Qur'an was revealed first?" He replied, "O you, wrapped-up' (Al-Muddaththir)." I said, "I have been informed that it was, 'Read, in the Name of your Lord who created (i.e. Surat Al-Alaq)...similar to the narration related by `Ali bin Al-Mubarak, 444 above).

Narrated Aisha:

The commencement of the Divine Inspiration to Allah's Messenger (ﷺ) was in the form of true dreams. The Angel came to him and said, "Read, in the Name of your Lord Who has created (all that exists), has created man a clot. Read! And your Lord is Most Generous" ..(96.1,2,3)

Narrated `Aisha:

The commencement of (the Divine Inspirations to) Allah's Messenger (ﷺ) was in the form of true dreams. The Angel came to him and said, "Read! In the Name of your Lord Who has created all exists), has created man from a clot. Read! And your Lord is Most Generous, Who has taught (the writing) by the pen. (96.1-4)