Sahih Bukhari Volume 001, Book 005, Hadith Number 283.
Narated By Abu Huraira : Allah's Apostle came across me and I was Junub He took my hand and I went along with him till he sat down I slipped away, went home and took a bath. When I came back. he was still sitting there. He then said to me, "O AbuHuraira! Where have you been?' I told him about it The Prophet said, "Subhan Allah! O Abu Huraira! A believer never becomes impure."