The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1066
Abu Huraira reported: The Messenger of Allah (may peace be upon him) said: I have been helped by terror (in the heart of the enemy) ; I have been given words which are concise but comprehensive in meaning; and while I was asleep I was brought the keys of the treasures of the earth which were placed in my hand.