Sayyiduna Khuzaymah bin Thabit (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) was asked about cleaning oneself after relieving oneself (istinja), and he (peace and blessings be upon him) said: "Three stones," but he forbade dung in them.
The Shaykh (may Allah have mercy on him) said that Ali bin al-Madini (may Allah have mercy on him) used to say: The narration of the group from Hisham from Amr bin Khuzaymah is the correct one.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 501