Sahih Muslim 606
صحيح مسلم#606SahihSalman reported that it was said to him:Your Apostle (ﷺ) teaches you about everything, even about excrement. He replied: Yes, he has forbidden us to face the Qibla at the time of excretion or urination, or cleansing with right hand or with less than three pebbles, or with dung or bone
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: 2:73