Sahih Muslim Book 6, Hadith Number 2434.

Chapter : It is forbidden to observe uninterrupted fasting.

Anas (Allah be pleased with him) reported that the Messenger of Allah (may peace be upon him) observed Saum Wisal during the early part of the month of Ramadan. The people among Muslims also observed uninterrupted fast. This (news) reached him (the Holy Prophet) and he said: Had the month been lengthened for me I would have continued observing Saum Wisal, so that those who act with forced hardness would (have been obliged) to abandon it. You are not like me (or he said): I am not like you. I continue to do so (in a state) that my Lord feeds me and provides me drink.