Revelation would come down upon the Messenger of Allah ﷺ on a cold morning, and his forehead would stream with sweat.
حدثنا أبو أسامة قال أخبرنا هشام عن أبيه
إن كان لينزل على رسول الله ﷺ في الغداة الباردة ثم تفيض جبهته عرقا
Its isnad is sahih. Muslim reported it, 4/1816, no. 2333, in "the Virtues." A similar version was reported by Bukhari, 1/18, no. 2, in "the Beginning of Revelation," Nasai, 2/147, no. 934, in "the Opening," and Humaydi, 1/124, no. 256.