Does tanning remove impurity from the hide of an animal whose flesh is unlawful to eat?
Chapter on Utensils
Al-Mughni
Book of Purification
Primary text
Tanning only has an effect on the hides of animals whose flesh is lawful to eat, and therefore the same ruling applies to what is analogized to it (i.e., slaughter). Even if we conceded that tanning purifies non-edible hides, it does not necessarily follow that slaughter also purifies, because tanning removes all impurities and moisture, making the skin suitable for preservation in a way that slaughter does not achieve; thus, tanning cannot be dispensed with in favor of slaughter.
Supporting text
The claim that tanning removes the established impurity is disputed, as it has been shown that the hide was never impure to begin with due to the primary arguments. Furthermore, slaughter does not prevent impurity if we assume impurity was established. This argument is further refuted by considering the slaughter performed by a Magian, a pagan, or someone in the state of Ihram, or by omitting the invocation of the name of God (Tasmiyah), or if the animal is cut in half before death.