When revelation descended upon Allah's Messenger (ﷺ) even during the cold days, his forehead perspired.
Sahih Muslim Book 43, Hadith 116
← Previous Hadith Umm Sulaim, what is this? She said: It is your sweat, which I put in my perfume. Allah's Apostle (ﷺ) sweated in cold weather when revelation descended upon him.

Sahih Muslim Book 43, Hadith 115 Next Hadith → How does the the wahi (inspiration) come to you? He said: At times it comes to me like the ringing of a bell and that is most severe for me and when it is over I retain that (what I had received in the form of wahi), and at times an Angel in the form of a human being comes to me (and speaks) and I retain whatever he speaks.

Sahih Muslim Book 43, Hadith 117