What is the ruling on the purity of two connected bodies of water, one or both being two qullahs in volume, when impurity is present?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
If either connected body measures two qullahs, neither becomes impure unless the impurity causes a change in its properties. This is because the volume of two qullahs repels impurity from itself and from what it contacts. If the impurity is in the river itself, and the river is two qullahs, both the river and the adjacent water remain pure under all circumstances. If the impurity is in the water less than two qullahs, that portion is impure before contact; upon meeting the larger body, it becomes pure due to connection, but reverts to impurity if separation occurs while the impurity remains.
Supporting text
If the impurity is in the body of water measured at two qullahs, it never becomes impure. If the still water is less than two qullahs, but combined with the flowing water they exceed two qullahs, and the impurity resides in the still water, neither becomes impure because the total volume exceeds two qullahs.