Sahih Bukhari
Sahih Bukhari Volume 001, Book 004, Hadith Number 146.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 04. Ablutions (Wudu')
Narated By Abu Aiyub Al-Ansari : Allah's Apostle said, "If anyone of you goes to an open space for answering the call of nature he should neither face nor turn his back towards the Qibla; he should either face the east or the west."