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)
Sahih al-Bukhari Book 65, Hadith 477
← Previous Hadith While Allah's Messenger (ﷺ) 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 Book 65, Hadith 476 Next Hadith → 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)

Sahih al-Bukhari Book 65, Hadith 478