Sahih Bukhari
Fasting
Volume: 003 / Book Number: 031 / Hadith Number: 166
Narrated Abu Ad-Darda:
We set out with Allah's Apostle on one of his journeys on a very hot day, and it was so hot that one had to put his hand over his head because of the severity of heat. None of us was fasting except the Prophet and Ibn Rawaha.