Sahih Bukhari Volume 008, Book 082, Hadith Number 801.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 82. Punishment of Disbelievers at War with Allah and his Apostle
Narrated By Abu Huraira : The Prophet said, "The one who commits an illegal sexual intercourse is not a believer at the time of committing illegal sexual intercourse and a thief is not a believer at the time of committing theft and a drinker of alcoholic drink is not a believer at the time of drinking. Yet, (the gate of) repentance is open thereafter."