Furthermore, does analogy require that water become impure when impurity mixes with it, or that it remain pure until the impurity becomes apparent? The scholars of our school and others hold two views on this.

Those who hold the first view say that water exceeding two qullahs is exempted because of hardship: it is difficult to prevent impurity from falling into it, since it is generally found in basins, pools, and wells. Small quantities, by contrast, are kept in vessels. This same consideration applies to flowing water, since protecting it from impurity is more difficult than protecting a large quantity of standing water.

For those who hold the second view—that the presumption is purity until impurity becomes apparent—the grounds for declaring flowing water pure are even stronger. A small quantity of standing water becomes impure because it may retain filth, as the hadith indicates. Flowing water, however, transforms filth through the force of its flow and therefore does not retain it, just as a large quantity of water does not retain it.

Accordingly, if urine, vomit, or anything else mixes with this water flowing through a bathhouse, this is impurity mixing with flowing water, which does not become impure unless its properties change. Our discussion concerns water in which impurity has not become apparent.

If it is said that bathhouse water becomes mixed with lote leaves, marsh mallow, earth, and other substances used to wash the head, as well as saltwort, soap, and henna,