Is it a condition for the validity of purification with stones (istijmar) that the excretions do not exceed their point of exit, such that if this occurs, istijmar is not sufficient and the use of water becomes necessary? What is the evidence for this, and is there a consensus on this condition?

The majority of scholars hold that istijmar (purification with stones or similar dry materials) is a concession applicable to the immediate area of the exit point and a small surrounding area. It is not sufficient for a large area beyond the exit point; rather, washing with water becomes obligatory in such cases. This is because istijmar is a concession due to general affliction (umoom al-balwa) only for what is commonly affected. Some scholars, however, dissented and were of the opinion that istijmar is sufficient absolutely, even if the impurity extends beyond the exit point, citing the generality of the evidence. This opinion holds strength, but the more cautious approach, to avoid differing opinions, is to use water if the excreted matter extends beyond the area it customarily reaches.