From Sahih Bukhari (Hadith 4954):
Narrated Jabir bin `Abdullah: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-Islamic period used to worship." After this the revelation started coming frequently and regularly
Reference: Bukhari 4954