Abu Dawud Book 1, Hadith Number 199.

Chapter : Performing ablution after awaking from sleep.

Narated By ‘Abd Allah b. ‘Umar : One night the Messenger of Allah (may peace be upon him) was busy and he delayed the night (‘isha’) prayer so much so that we dosed in the mosque. We awoke, then dozed, and again awoke and again dozed. He (the Prophet) then came upon us and said : There is none except you who is waiting for prayer.