It is narrated from Hazrat Anas (may Allah be pleased with him) that once the Prophet (peace and blessings be upon him) observed continuous fasting (Saum Wisal) at the end of a month. Some people also did the same. When the Prophet (peace and blessings be upon him) was informed of this, he said: "If this month had been longer, I would have continued fasting for so many days that those who go to extremes in religion would abandon their extremism. I am not like you; my Lord gives me food and drink."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 13656