Sahih Muslim Book 001, Hadith Number 0343.
Chapter : Pertaining to his (Prophet's) words: He is a Light; how could I see Him?-and his words: I saw the Light.
Abu Musa reported: The Messenger of Allah (may peace be upon him) was standing amongst us and he told us five things. He said: Verily the Exalted and Mighty God does not sleep, and it does not befit Him to sleep. He lowers the scale and lifts it. The deeds in the night are taken up to Him before the deeds of the day. and the deeds of the day before the deeds of the night. His veil is the light. In the hadith narrated by Abu Bakr (instead of the word "light") it is fire. If he withdraws it (the veil), the splendour of His countenance would consume His creation so far as His sight reaches.