Sunan Abi Dawud 7
سنن أبي داود#7SahihNarrated Salman al-Farsi: It was said to Salman: Your Prophet teaches you everything, even about excrement. He replied: Yes. He has forbidden us to face the qiblah at the time of easing or urinating, and cleansing with right hand, and cleansing with less than three stones, or cleansing with dung or bone
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Muslim (262)
In-book reference: 1:7