What is the ruling regarding the necessity of pouring out impure water when the identity of the impure container is known?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
When the identity of the impure water is known, it is recommended to pour it out to remove self-doubt. If drinking is necessary, one drinks from the certainly pure water and performs *Tahammum* if only the impure water remains. If there is a fear of thirst later, the correct position is to retain the pure water and perform *Tahammum*, because the existence of the impure water is treated as non-existence when immediate drinking is required, and the fear of future thirst justifies *Tahammum* just as immediate necessity does.
Supporting text
The view of the Judge is that one should perform *Wudu* with the pure water and retain the impure water, as there is no immediate need to drink the latter, thus *Tahammum* is not permitted while pure water exists.