For that which is adjacent to a large amount of impurity is a large amount of water, so it does not become impure, while that which is adjacent to a small amount of impurity is a small amount of water, so it becomes impure. For if we were to imagine a dog on one side of a river, with one of its hairs on the other side, the water adjacent to the hair would not reach two qullahs, due to the small amount of what is adjacent to it, while the water adjacent to the dog would reach [the volume of] qullahs. Al-Qadi and Ibn Aqil mentioned that the 'flow' (jiryah) adjacent to the impurity is between the two banks of the river, and it is necessary to interpret it as we have described, based on what we have explained.

If it is said: This leads to equating a large amount of impurity with a small amount.

We say: The Law has equated them in stagnant water, which is the foundational principle (asl), so it is necessary to equate them in flowing water, which is a derivative (far').

Section: If there is stationary water on the side of the river, leaning away from the course of the water yet connected to the flowing water, or if there is a depression (wahdah) in the riverbed containing stationary water, and that is [together] with the 'flow' corresponding to it less than two qullahs, both become impure due to the presence of impurity in one of them; because it is connected water that is less than two qullahs, so it all becomes impure because of it, like stagnant water. If one of the two is [equivalent to] two qullahs, neither one of them becomes impure as long as they remain connected, unless it is altered; because two qullahs repel impurity from themselves and from what they come into contact with. Then, one must consider whether the impurity is in the river or in the stationary water. If it is in the river and it is two qullahs, it is pure in any case, and likewise is the stationary water. If it is less than two qullahs, it is impure before it meets the stationary water, but when it is adjacent to it, it becomes pure due to its connection with it; and when it separates from it, it returns to being impure due to its small amount while the impurity is present in it. If the impurity is in the stationary water, it does not become impure under any circumstances, because it and what it comes into contact with remains [a volume of] two qullahs. If the stationary water is less than two qullahs, and the 'flow' is likewise, but together they exceed two qullahs, and the impurity is in the stationary water, neither one of them becomes impure, because it, with what it comes into contact with, is more than two qullahs. If the impurity is in the river, then the analogy of our companions' position is that the stationary water becomes impure, as does the 'flow' containing the impurity, and everything that passes by the stationary water thereafter; because the 'flow' containing the impurity was impure before it met the stationary water, then the stationary water became impure by it, because it is water less than two qullahs that was reached by impure water, and the 'flow' did not become pure.