What is the minimum requirement for purification by stones (Istijmaar)?
Chapter on Cleaning oneself (Istitabah) and Impurity (Hadath)
Al-Mughni
Book of Purification
Primary text
It is established that one must use no less than three stones for purification. The Prophet, peace be upon him, commanded this: 'No one among you should perform Istinjaa with less than three stones,' narrated by Muslim. The command implies obligation, and the reference to sufficiency ('tajzi'uhu') is applicable only to that which is obligatory. Furthermore, the prohibition against using fewer than three implies that abandoning the entire act is a greater offense.
Supporting text
The statement indicating 'no blame' (la haraj) in performing Istijmaar relates only to the discretionary aspect of performing an odd number (Witr), not to the fundamental requirement of performing Istijmaar itself. Wiping (as an alternative to washing) is permitted due to the difficulty associated with the frequent need for washing in the area of Istinjaa.