In claims against a slave, who is the proper party to the dispute regarding matters where the slave's statement against himself is accepted?

Primary text

If a claim is made against a slave concerning matters where the slave's testimony against himself is accepted, such as retribution (*qisas*), divorce (*talaq*), or slander (*qadhf*), the dispute lies solely with the slave, not his master. If an oath is prescribed for such matters, the slave swears, and if he refuses, no one else swears in his stead.