Sahih Muslim 607
صحيح مسلم#607SahihSalman said that (one among) the polytheists remarked:I see that your friend even teaches you about the excrement. He replied; Yes, he has in fact forbidden us that anyone amongst us should cleanse himself with his right hand, or face the Qibla. He has forbidden the use of dung or bone for it, and he has also instructed us not to use less than three pebbles (for this purpose)
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: 2:74