Sahih Bukhari Volume 007, Book 062, Hadith Number 127.
Narrated By 'Abdullah bin 'Amr bin Al-'As : Allah's Apostle said, "O 'Abdullah! Have I not been formed that you fast all the day and stand in prayer all night?" I said, "Yes, O Allah's Apostle!" He said, "Do not do that! Observe the fast sometimes and also leave them (the fast) at other times; stand up for the prayer at night and also sleep at night. Your body has a right over you, your eyes have a right over you and your wife has a right over you."