Sunan Abu-Dawud, Book 1, Number 0041:
Quote:
Narrated Khuzaymah ibn Thabit:
The Prophet (peace_be_upon_him) was asked about cleansing (after relieving oneself). He said: (One should cleanse oneself) with three stones which should be free from dung.
Could you develop blisters if you use stones to wipe your buttock?