Musnad Ahmad 27:274

Yahya narrated to us, from Ubaydullah, Nafi’ narrated to me, from Abdullah ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) fasted continuously (without breaking his fast at night) during Ramadan, so the people fasted continuously. They said: "You forbade us from fasting continuously, yet you fast continuously." He said: "I am not like any one of you; I am fed and given to drink."