Musnad Ahmad 1074:1

'Abd al-Rahman narrated to us, Malik narrated to us, from Sumayy, from Abu Bakr ibn 'Abd al-Rahman, from one of the companions of the Prophet, may Allah bless him and grant him peace: "The Prophet, may Allah bless him and grant him peace, was seen at al-'Arj, and he was pouring water over his head due to the heat or due to thirst, while he was fasting."