Sahih Bukhari
Sahih Bukhari Volume 001, Book 008, Hadith Number 391.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 08. Prayers (Salat)
Narated By Ibn Abbas : When the Prophet entered the Ka'ba, he invoked Allah in each and every side of it and did not pray till he came out of it, and offered a two-Rak'at prayer facing the Ka'ba and said, "This is the Qibla."