Harith bin Hisham asked the Messenger of Allah ﷺ, "How does the revelation come to you?"The Messenger of Allah ﷺ replied, "Sometimes it comes to me like the ringing of a bell, and that is the hardest on me. Then it leaves me, and I have grasped what was said. And sometimes the angel appears to me in the form of a man and speaks to me, and I grasp what he says."Ayesha said, "I saw the revelation descending upon him on a bitterly cold day, and when it left him, his forehead was streaming with sweat."
أخبرنا محمد بن سلمة والحارث بن مسكين قراءة عليه وأنا أسمع واللفظ له عن ابن القاسم قال حدثني مالك عن هشام بن عروة عن أبيه
أن الحارث بن هشام سأل رسول الله ﷺ كيف يأتيك الوحي فقال رسول الله ﷺ أحيانا يأتيني في مثل صلصلة الجرس وهو أشده علي فيفصم عني وقد وعيت ما قال وأحيانا يتمثل لي الملك رجلا فيكلمني فأعي ما يقول قالت عائشة ولقد رأيته ينزل عليه في اليوم الشديد البرد فيفصم عنه وإن جبينه ليتفصد عرقا
Bukhari narrated it in the Book of the Beginning of Revelation, in the chapter on how revelation began to come to the Messenger of Allah ﷺ and so on, hadith no. 2, from the hadith of Malik, with this wording. It is also found in Muwatta (Yahya) 1/202, 203, and in Kubra, hadith no. 1006. Muslim also narrated it, hadith no. 2333, through another route from Hisham, with this wording. See the previous hadith.