It is narrated from Sayyiduna Khuzaymah bin Thabit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "In cleansing oneself after relieving oneself (istinja), three stones in which there is no dung (are sufficient)."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3710