The second reason is that the jars of Hajar were the largest of the jars and the most well-known during the era of the Prophet (may the peace and blessings of Allah be upon him). Al-Khattabi mentioned this, saying: "They are of a well-known manufacture and a known capacity. They do not vary, just as the sa' measures and dry measures do not vary, because a legal limit cannot be established upon something unknown." Abu 'Ubayd said: "They are the hiban (earthen jars), and they are widely known and recognized, so the term 'two qullahs' should be interpreted based upon them due to their fame and size. For any countable item set as a singular measure refers only to the largest of its type, as it is closer to certainty and fewer in number. For this reason, the zakat threshold was established based on the awsuq (loads), not the aswu' (sa's) or the amdad (mudds)."

This issue clearly indicates by its explicit wording that if water reaches the amount of two qullahs and does not change due to impurities falling into it, it does not become impure. Its implied meaning indicates that if water changes due to impurity, it becomes impure even if it is a large quantity, and that water less than two qullahs becomes impure merely by contact with impurity, even if it does not change.

As for the impurity of water that has changed due to impurity, there is no disagreement regarding it. Ibn al-Mundhir said: "The people of knowledge have reached a consensus that if a small or large amount of water has an impurity fall into it, and it changes the water's taste, color, or odor, it is impure as long as it remains in that state." Abu Umamah al-Bahili reported that the Prophet (may the peace and blessings of Allah be upon him) said: "Water is pure; nothing makes it impure except that which overcomes its odor, taste, or color." Narrated by Ibn Majah (17). Harb ibn Isma'il said: Ahmad was asked about water if its taste or odor changes (18). He replied: "One should not perform ablution with it nor drink it, and there is no hadith regarding it. However, Allah the Exalted has forbidden carrion, so if carrion is in water and its taste or odor changes, that is the taste and odor of the carrion."