For excessive strictness regarding impurities, both in kind and amount, is the religion of the Jews, while undue leniency is the religion of the Christians. Islam follows the middle course; therefore, any position that partakes of this moderation is closer to the religion of Islam.

[Mixing the Lawful with the Unlawful Is Like Mixing a Pure Liquid with an Impure One]

Another foundational principle concerns the mixing of the lawful with the unlawful, like mixing a pure liquid with an impure one. The severity of the Kūfan position on this matter is unmistakable.

The rationale underlying their position is that they treat water like all other liquids: if impurity falls into a liquid, it cannot be used without also using [that which is impure], and so the whole is prohibited, [even though deeming] liquids other than water impure is supported by only a few transmitted reports.

Opposing them are Mālik and other scholars of Medina. According to their well-known position, water becomes impure only when its properties change, and they do not prohibit the use of water that has already been used or any other kind of water. In this way, they give the fullest effect to water’s purifying capacity, while distinguishing it from other liquids.

Ahmad also has a position corresponding to theirs. The position most commonly reported from him, however, follows a middle course by distinguishing between small and large quantities of water, as does al-Shāfiʿī.

Reports from Ahmad also differ concerning liquids other than water: are they treated like water, or are they not treated like it, as Mālik and al-Shāfiʿī hold? Or is a distinction drawn between liquids that are water-like and those that are not, such as grape vinegar? There are three reports.

These positions plainly embody moderation in terms of both transmitted evidence and rational analysis, while Ahmad’s position agreeing with Mālik has the stronger evidential basis.

[Parts of a Carcass That Contain No Moisture, Such as Hair, Nails, and Feathers]

Another foundational principle is that people hold differing positions regarding parts of a carcass that contain no moisture—such as hair, nails, and feathers—as to whether they are pure or impure. There are three positions.