The underlying question in this issue is whether mixing foul matter—that is, impurity—with water renders all of it unlawful, or whether the impurity has been transformed within the water and therefore no longer has any legal effect. Those who consider the water impure adopt the former view.

Those who exempt large quantities argue that it is difficult to prevent impurity from falling into such water. They therefore treat this as a case for juristic preference, as do some followers of al-Shāfi‘ī and Ahmad. The followers of Abū Hanīfah, however, base the ruling on whether or not the impurity reaches the water in question. They determine this by movement or by the dimensions of length and breadth, without considering depth.

The correct position is the first view: whenever the impurity is known to have undergone transformation, the water is pure, whether its quantity is small or large. The same applies to all liquids. This is because Allah Most High has permitted wholesome things and forbidden foul things, and foul things are distinguished from wholesome things by their characteristics. Thus, when water or another substance has the characteristics of something wholesome rather than something foul, it must be classified as lawful, not unlawful.

Furthermore, it is established in the hadith of Abū Sa‘īd that the Prophet, may Allah bless him and grant him peace, was asked: “May we perform ablution with water from the well of Budā‘ah?” It was a well into which menstrual cloths were thrown