Wudhu Before Sleeping (Hadith No. 284)
Volume 1, Book 5, Number 284:
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).
If you’ve tried it, you know how it feels. I don’t know if it has any scientific benefits or not, but I know this: Prophet (SAW) made extra effort to stay clean and pure and he loved being in the state of wudhu. Isn’t it all that matters?