Al-Matalib al-'Aliyah 146 — Wudu after sleep

It is narrated from Hajjaj that he mentioned before (Imam) Ata bin Abi Rabah (may Allah have mercy on him) the state of the sleep of the Prophet (peace and blessings be upon him): that he (peace and blessings be upon him) would (at times) sleep so deeply that the heavy sound of his (peace and blessings be upon him) breathing could be heard, then he (peace and blessings be upon him) would (wake up and) pray (without a fresh ablution). At that Ata (may Allah have mercy on him) said: "The Prophet (peace and blessings be upon him) was not like other people (in the matter of ablution remaining intact during sleep)."
Imam Abu Ya'la narrated this narration in his Musnad. Although its narrator Hajjaj bin Artat is criticised with regard to his memory, its content fully agrees with the authentic hadith of Sahih al-Bukhari and Sahih Muslim which state explicitly that the pure heart of the Prophet (peace and blessings be upon him) remained awake; that is why his (peace and blessings be upon him) sleep did not invalidate ablution as the sleep of other people does.