What is the ruling on transformation (istihalah) in foods, such as mixing a small amount of a forbidden substance with a large quantity of a pure substance? And are liquids such as oil, vinegar, and milk measured like water in terms of purity if they reach two qullas? And what is the criterion for transformation (istihalah)?

"Istihalah" (transformation) is the change of a thing's reality into another reality, such as the transformation of wine into vinegar. According to the jurists:

- Hanafis: It is the change of the substance and the reversal of its reality into another reality.

- Shafi'is: It is the transformation of a thing from one state to another.

- Malikis: It is the material's change from its attributes and its departure from the name it had, to attributes and a name specific to it.

Scholars have agreed upon the purity of wine if it transforms into vinegar without human intervention. However, they differed on the purity of other impurities through istihalah.

As for a pure liquid that does not change upon contact with impurity, it remains pure. This is the view of Sheikh al-Islam Ibn Taymiyyah, al-Zuhri, and al-Bukhari, a narration from Malik, and the madhhab of Abu Hanifah.