Musnad Abu Ya'la al-Mawsili 42:107

From Abu Nadra, from Abu Sa’id, who said: The Prophet, may Allah bless him and grant him peace, passed by a river of water while he was on a mule, and the people were fasting, and the pedestrians were many. He said: "Drink." So they began to look at him. He said: "Drink, for I am the easiest of you." So they began to look at him, and he turned his hip and drank, and the people drank.