Sahih Muslim Book 004, Hadith Number 1671.
Chapter : Encouragement to observe prayers during Ramadhan and that is Tarawih.
Ibn 'Abbas reported: I spent a night with my material aunt (sister of my mother) Maimuna. The Apostle of Allah (may peace be upon him) got up during the night and relieved himself, then washed his face and hands and went to sleep. He then got up again, and came to the water skin and loosened its straps, then performed good ablution between the two extremes. He then stood up and observed prayer. I also stood up and stretched my body fearing that he might be under the impression that I was there to find out (what he did at night). So I also performed ablution and stood up to pray, but I stood on his left. He took hold of my hand and made me go round to his right side. The Messenger of Allah (may peace be upon him) completed thirteen rak'ahs of his night prayer. He then lay down and slept and snored (and it was his habit to snore while asleep). Then Bilal came and he informed him about the prayer. He (the Holy Prophet) then stood up for prayer and did not perform ablution, and his supplication included there words: "O Allah, place light in my heart, light in my sight, light in my hearing, light on my right hand, light on my left hand, light above me, light below me, light in front of me, light behind me, and enhance light for me."
Kuraib (the narrator) said: There are seven (words more) which are in my heart (but I cannot recall them) and I met some of the descendants of 'Abbas and they narrated these words to me and mentioned in them: (Light) in my sinew, in my flesh, in my blood, in my hair, in my skin, and made a mention of two more things.