An example of this is the report established in the Sahīh that the Messenger of Allah, may Allah bless him and grant him peace,

“Was asked about a mouse that had fallen into ghee. He said: ‘Remove it and the ghee around it, and eat the rest of your ghee.’”

There is agreement that the ruling is not exclusive to that particular mouse and that particular ghee; rather, it applies more broadly. The question therefore remains: what is the basis on which the ruling depends? Some scholars claim that the ruling applies exclusively to a mouse falling into ghee. They therefore regard ghee into which a mouse has fallen as impure without qualification, but do not regard ghee as impure when a dog, urine or excrement falls into it. Nor do they regard oil and similar substances as impure when a mouse falls into them. This opinion is unquestionably mistaken.

This does not depend on whether legal analogy is authoritative. The disputed form of analogy involves deriving the basis of the ruling: that is, where it is possible that the ruling applies exclusively to the case addressed by the text. If the ruling could be exclusive to that case, but could also apply both to it and to other cases, someone employing analogy must establish that the feature shared by the original case and the new case is the basis of the ruling. An example is his saying:

“Do not sell gold for gold except in equal amounts; do not sell silver for silver except in equal amounts; do not sell barley for barley except in equal amounts; and do not sell salt for salt except in equal amounts.”

When he prohibited exchanging unequal amounts of commodities such as these, the prohibition could have been based on a shared feature or on a feature peculiar to them.

But when he was asked about a mouse that had fallen into ghee, he gave an answer concerning that