What is the ruling on the right to Qisas (retaliation in kind) if a slave commits an injury upon a free person equal to Qisas, and the injured party purchases the slave for the value of the injury (Arsh)?

Primary text

If a slave inflicts an injury upon a free person necessitating Qisas, and the injured party purchases the slave for the amount of the *Arsh* (the compensatory value of the injury), the right to Qisas is forfeited. This is because the choice to resort to purchasing the slave is an election for monetary compensation (*Al-Mal*). The subsequent purchase itself is invalid if the precise value of the *Arsh* is unknown to both parties, as the price (*thaman*) would be unknown, rendering the contract void. Furthermore, even if the number and age of the camels owed are known, if their specific description or quality (*sifa*) is unknown, this is treated as ignorance of the substance itself, which invalidates the sale.