Musnad Ahmad 1018:130

'Uthman ibn 'Umar narrated to us, Malik informed us, from Sumayy, from Abu Bakr ibn 'Abd al-Rahman ibn al-Harith, from a man among the companions of the Prophet, may Allah bless him and grant him peace, that the Messenger of Allah, may Allah bless him and grant him peace, fasted during his journey in the year of the Conquest, and he ordered his companions to break their fast and said: "You are going to meet your enemy, so gain strength." It was said: "O Messenger of Allah, the people have fasted because of your fasting." When he reached al-Kadid, he broke his fast. The one who narrated to me said: I saw the Messenger of Allah, may Allah bless him and grant him peace, pouring water over his head because of the heat while he was fasting.