Musnad Ahmad 30:212

Sufyan narrated to us, from Abu al-Zinad, from al-A'raj, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Beware of continuous fasting (wisal)." They said: "O Messenger of Allah, you practice continuous fasting." He said: "I am not like any one of you; I spend the night while my Lord feeds me and gives me to drink."