Musnad Abu Ya'la al-Mawsili 155:248

On the authority of Abu Hurayrah, he said: The Messenger of Allah (ﷺ) said: "Beware of *wisal* (continuous fasting without breaking it at night)," three times. They said: "O Messenger of Allah, you practice *wisal*." He said: "You are not like me in that. I spend the night while my Lord feeds me and gives me to drink. Take upon yourselves of deeds that which you can bear."