Sahih Bukhari
Ablutions (Wudu)
Volume: 001 / Book Number: 004 / Hadith Number: 150
Narrated 'Abdullah bin 'Umar:
I went up to the roof of Hafsa's house for some job and I saw Allah's Apostle answering the call of nature facing Sham (Syria, Jordan, Palestine and Lebanon regarded as one country) with his back towards the Qibla. (See Hadith No. 147).