Sahih al-Bukhari 148
صحيح البخاري#148SahihNarrated `Abdullah bin `Umar:I went up to the roof of Hafsa's house for some job and I saw Allah's Messenger (ﷺ) 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)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:14