It was narrated that `A'ishah said:
"The Messenger of Allah would fall asleep until he was breathing deeply, then he would get up and offer the prayer, and he did not perform ablution." (Hasan)Tanafisi said: "Waki` said: 'She meant while he was prostrating (he would sleep).'" (IT)
English reference (IT): Vol. 1, Book 1, Hadith 474 (IT)
Arabic reference (IT): Book 1, Hadith 512 (IT)