Sahih al-Bukhari 138

It is narrated from ibn 'Abbas, "The Prophet, may Allah bless him and grant him peace, slept to the extent that he snored and then prayed," or he said, "He lay down to the extent that he snored and then got up and prayed." Later on Sufyan reported the same incident reported the same incident repeatedly that 'Amr related from Kurayb saying that Ibn 'Abbas said, "Once I spent the night in the house of my aunt, Maymuna, and the Prophet, may Allah bless him and grant him peace, got up during the night. After some of the night had passed, the Prophet got up and did wudu' lightly from a hanging waterskin - 'Amr (one of the narrators) described it as being light and used little water - and stood up to pray. I did wudu' as the Prophet, may Allah bless him and grant him peace, had done and then went and stood on his left. (Sufyan might have said shimalihi rather than yasarihi) He moved me to his right and then prayed as much as Allah willed and then lay down and went to sleep to the extent that he snored. Then the caller came and announced the prayer, then the Prophet went with him for the prayer and he prayed without doing wudu'. Sufyan said, "We said to 'Amr that some people say, 'The eyes of the Messenger of Allah, may Allah bless him and grant him peace, sleep but his heart does not sleep.'" 'Amr said that he heard 'Ubayd ibn 'Umayr say, "The dreams of the Prophets are revelation." Then he recited [the conversation of Ibrahim to Isma'il], "I saw in a dream that I must sacrifice you." (37:102)