What is the guarantor's liability for an increase in the value of a usurped item due to maturation (fattening), learning (acquiring a skill), or other means?
General Chapter
Al-Mughni
Book of Usurpation
Primary text
If a usurped item increases in value, such as an animal fattening, or if a slave acquires knowledge or skill (taʿallum or ṣināʿa), the usurer is liable for the resulting increase in value, even if this increase makes the item’s value double, according to Imam Ahmad and Al-Shafi'i. This increase is treated as an increase in the essence of the usurped item. If the item later decreases in value due to bodily deterioration or forgetting the learned skill, the owner takes the item in its current state, and the usurper is liable for the difference between the value at the time of usurpation and the final diminished value.
Supporting text
Abu Hanifa and Malik hold that the usurper is not obligated to compensate for the increase in value unless the owner demands the return of the item with the increase, in which case the owner must return the item as taken, as they are not responsible for a decrease in market price. Our position maintains liability because the increase is an increment to the usurped object itself, necessitating the usurper's guarantee, just as if the owner had demanded its return and the usurper failed to do so. This is distinguished from an increase in market price, which would not be guaranteed if it existed at the time of usurpation.