Sunan an-Nasa'i

It was narrated from Aishah that: Al-Harith bin Hisham asked the Messenger of Allah (ﷺ): “How does the Revelation come to you?' He said: “Like the ringing of a bell, and this is the hardest on me. When it departs I remember what he said. And sometimes the Angel appears to me in the form of a man and speaks to me, and I remember what he said." Aishah said: "I saw him when the Revelation came to him on a very cold day, and his forhead was dripping with sweat””