The Hadith (Inspired Sayings) of Muhammed
Impurity -- Sahih Buhari-- Volume 1, Book 5, Number 281:
Narrated Abu Huraira: The Prophet came across me in one of the streets of
Medina and at that time I was Junub. So I slipped away from him and went
to take a bath. On my return the Prophet said, "O Abu Huraira! Where have
you been?" I replied, "I was Junub, so I disliked to sit in your company."
The Prophet said, "Subhan Allah! A believer never becomes impure."
Narrated Abu Salama : I asked 'Aisha "Did the Prophet use to sleep while he was Junub?" She replied, "Yes, but he used to perform ablution (before going to bed).
Junub -- Volume 1, Book 5, Number 286:
Narrated 'Aisha (wife of Muhammed): Whenever the Prophet intended to sleep while he was Junub, he used to wash his private parts and perform ablution like that for the prayer.