Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: I stayed one night with my maternal aunt, Sayyidah Maymunah (may Allah be pleased with her). When part of the night had passed, the Prophet (peace and blessings be upon him) got up, and he (peace and blessings be upon him) performed a light ablution from a hanging water-skin (Amr described it as light and very little). Then he stood up to pray, so I also got up. I performed ablution just as he (peace and blessings be upon him) had performed ablution, then I stood on his (peace and blessings be upon him) left side, and he (peace and blessings be upon him) turned me around and placed me on his right. Then he prayed as much as Allah willed, then he lay down and slept until he snored. Then the caller came and informed him (peace and blessings be upon him) about the prayer.
On another occasion Sufyan narrated: Then he (peace and blessings be upon him) stood up for the prayer and led us in prayer, but did not perform ablution.
Sufyan said: We said to Amr: People say, "The eyes of the Prophet (peace and blessings be upon him) sleep but his heart does not sleep." Amr said: I heard Ubayd bin Umayr (may Allah have mercy on him) say: The dreams of the prophets are revelation, and as evidence he recited this verse: "Indeed, I have seen in a dream that I am slaughtering you" [Surah al-Saffat: 102].
(b) In Bukhari and Muslim it is stated that Sufyan said: This was specific to the Prophet (peace and blessings be upon him), because a saying of his (peace and blessings be upon him) has reached us which is evidence for us that "his (peace and blessings be upon him) eyes sleep but his heart does not sleep."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 601