The Book Pertaining to Paradise, Its Description, Its Bounties and Its Intimates (Kitab Al-Jannat wa Sifat Na'imiha wa Ahliha)
Muslim :: Book 40 : Hadith 6807
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: Saihan, Jaihan, Euphrates and Nile are all among the rivers of Paradise.