He means by al-masani' (cisterns): the basins that were constructed as a water source for the pilgrims to drink from, in which a large amount of water gathers that suffices them and has a surplus; such [water] is not rendered impure by any filth as long as it has not changed. We do not know anyone who disagreed on this. Ibn al-Mundhir said: The scholars have reached a consensus that when a large body of water, such as an arm (khalij) of the sea and the like, is contaminated by an impurity, and it does not alter its color, taste, or odor, it remains in its original state and purification can be performed with it. As for that which can be drained when it reaches two qullatayn (two large earthen vessels), it is not rendered impure by any impurities except for human urine or liquid excrement; for there are two narrations from Ahmad regarding this, the most famous of which is that it becomes impure as a result.

A similar view is reported from Ali and al-Hasan al-Basri. Al-Khallal said: We were told on the authority of Ali, may Allah be pleased with him, with a sound isnad, that he was asked about a boy who urinated in a well, and he ordered them to drain it. Similar reports are narrated from al-Hasan al-Basri.

The rationale for this is what Abu Hurayrah reported from the Prophet (peace and blessings of Allah be upon him), that he said: "Let none of you urinate in stagnant water that does not flow, then perform wudu (ablution) from it." Agreed upon. In another wording: "Then perform wudu from it." It is Sahih (authentic). In al-Bukhari: "Then perform ghusl (full washing) in it." This encompasses both small and large quantities, and it is specific regarding urine, and it is more authentic than the hadith of the two qullatayn, therefore it is necessary to prioritize it.

The second narration is that it does not become impure as long as it has not changed, like all other impurities; this was chosen by Abu al-Khattab and Ibn Aqil. This is the school of al-Shafi'i, and the majority of scholars do not differentiate between urine and other types of impurities, based on the saying of the Prophet (peace and blessings of Allah be upon him): "When water reaches two qullatayn, it does not become impure." Furthermore, because the impurity of human urine is not greater than the impurity of a dog's urine, and [the latter] does not render the two qullatayn impure, so human urine is even more so. The hadith of Abu Hurayrah must be restricted by the evidence regarding that which cannot be drained, so that which reaches two qullatayn is measured by it, or it [the hadith of Abu Hurayrah] is restricted by the hadith of the two qullatayn; for restricting it by a hadith of the Prophet (peace and blessings of Allah be upon him) is better than restricting it by mere opinion and arbitrary judgment without evidence. Moreover, if the two hadiths were equal [in weight], it would be necessary to defer to analogy based on other impurities.