Maliks Muwatta Book 18, Hadith Number 39.

Section : The Prohibition against Fasting for Two Days or More without Breaking the Fast in between (Wisal).

Yahya related to me from Malik from Abu’z-Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, “Beware of wisal. Beware of wisal.” They said, “But you practise wisal, Messenger of Allah.” He replied, “I am not the same as you. My Lord feeds me and gives me to drink.”