Is it permissible to complete insufficient water for purification with another liquid that has not changed its properties?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
It is permissible to use water mixed with another liquid, provided the liquid does not alter the water, if the total amount is insufficient for purification alone. This permission is supported by one of the two established narrations. The reasoning is that the mixture remains pure and does not prevent the validity of the purification, similar to a situation where the original amount of water was already sufficient for purification. The ruling is that since the characteristic of the added liquid does not manifest upon the water, the entire mixture retains the legal status of water.
Supporting text
A second view prohibits this action based on the certainty that some parts of the limbs are washed by the added liquid. However, this objection is invalidated by noting that even if the original water was sufficient, mixing it with a liquid and then performing ablution with the mixture—even if the remaining liquid is equal to or less than the original water amount—is permissible, despite the certainty that both the water and the added liquid were used in the process, due to the impossibility of separating the water from the added liquid.