Musnad Ahmad 31:261

Yunus narrated to us, Hammad—meaning Ibn Zayd—narrated to us, Bishr ibn Harb narrated to us, he said: I heard Abu Sa’id al-Khudri saying: The Messenger of Allah (peace and blessings of Allah be upon him) forbade *al-wisal* (continuous fasting without breaking it). It was said: "O Messenger of Allah, why do you do it yourself?" He said: "I am not like one of you; I am fed and given to drink."