عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ إِنْ كَانَ لَيَنْزِلُ عَلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فِي الْغَدَاةِ الْبَارِدَةِ ثُمَّ تَفِيضُ جَبْهَتُهُ عَرَقًا
It is narrated from Sayyida Aisha (may Allah be pleased with her), she says: On a cold morning, revelation would descend upon the Messenger of Allah (peace and blessings be upon him), but even then, sweat would begin to flow from his forehead.