Sayyiduna Salman al-Farisi (may Allah be pleased with him) said: The polytheists said: We see that your companion teaches you, even to the point of teaching you the etiquette of relieving yourselves! He said: He forbids us to face the qiblah when relieving ourselves, and for any of us to clean himself (istinja) with his right hand; and he forbade us (to clean ourselves) with dung and bones, and he said: "Less than three stones will not suffice any of you."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6054