The answer is that its color is presumed to differ from that of water. Thus, if it is assumed that it changes the water’s color, then we rule the water impure. Moreover, it will generally be its odor that changes the odor of the water, and likewise its taste.

As for the hadith of the two qullahs, the scholars have differed over whether it is authentic or weak. Those who consider it weak find no conflict between it and the hadith, “Water is purifying; nothing renders it impure,” because weak evidence cannot establish a proof.

According to the view that it is authentic, it may be said that it has both an explicit meaning and an implied meaning. Its explicit meaning is that, when water reaches two qullahs, it is not rendered impure. This is not unrestricted, however, since water that is changed by an impurity is excluded: it is impure by consensus.

Its implied meaning is that water below two qullahs becomes impure. It may be answered that it becomes impure if it is changed by the impurity, because the explicit meaning of the hadith, “Water is purifying; nothing renders it impure,” takes precedence over this implication. An implication may be fulfilled in only one case, and here it is fulfilled where the water has changed.

As for citing the Prophet’s ﷺ words, “None of you should urinate in standing water and then bathe in it,” as evidence for distinguishing between human urine and feces and other impurities, it may be said: the Prophet ﷺ did not say that it renders the water impure. Rather, he prohibited a person from urinating in it and then bathing in it—not because it is impure, but because it is not reasonable for someone to use it as a urinal and then return to bathe in it. This is like his ﷺ saying: “None of you should flog his wife as a slave is flogged, then lie with her” (1),