None of you should clean himself with less than three stones

Salmān al-Fārisi (may Allah be pleased with him) reported: The polytheists mockingly said to us: Your Prophet teaches you everything; he even teaches you how to relieve yourselves, whether in urinating or defecating! Salmān said: Yes, he taught us the etiquette of relieving oneself. Among what he taught us is that he (may Allah's peace and blessings be upon him) forbade us from cleaning ourselves with the right hand after relieving ourselves, out of respect and to keep it clean from impurity.

He also forbade us from facing the Ka‘bah while urinating or defecating. And he forbade us from using animal dung or bones for Istijmār (dry cleansing). Furthermore, he instructed that one in a state of Hadath (ritual impurity) should not suffice with fewer than three stones when performing Istijmār.