Jami' al-Tirmidhi

Abdur-Rahman bin Yazld said, : "They said to Salman, 'Your Prophet taught you about everything, even defecating?' So Salman said, 'Yes. He prohibited us from facing the Qiblah when defecating and urinating, performing Istinja with the right hand, using less than three stones for Istinja, and using dung or bones for Istinja"