Sahih Muslim 610
صحيح مسلم#610SahihAbu Huraira said:When any one amongst you squats for answering the call of nature, he should neither turn his face towards the Qibla nor turn his back towards it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 2:77