Sunan Ibn Majah, Chapter: The Chapters of Purification and its Sunnah

Salman said that one of the idolaters said to him, while they were making fun of him: "I see that your companion (the Prophet (saw)) is teaching you everything, even how to relieve yourselves?" He said: "Yes indeed. He has ordered us not to face the Qiblah (prayer direction) nor to clean ourselves with our right hands, and not to be content with anything less than three stones, which are not to include any excrement or bones." (Sahih)