Sahih Bukhari, Chapter: Characteristics of Prayer

One night I slept at the house of my aunt Maimuna and the Prophet slept (too). He got up (for prayer) in the last hours of the night and performed a light ablution from a hanging leather skin. ('Amr, the sub-narrator described that the ablution was very light). Then he stood up for prayer and I got up too and performed the ablution in the same way and joined him on his left side. He pulled me to the right and prayed as much as Allah will. Then he lay down and slept and I heard his breath sounds till the Mu'adh-dhin came to him to inform him about the (Fajr) prayer. He left with him for the prayer and prayed without repeating the ablution. (Sufyan the subnarrator said: We said to 'Amr, "Some people say, 'The eyes of the Prophet sleep but his heart never sleeps.' " 'Amr said, "'Ubai bin 'Umar said, 'The dreams of the Prophets are Divine Inspirations. Then he recited, '(O my son), I have seen in dream that I was slaughtering you (offering you in sacrifice).") (37.102)