Musannaf Ibn Abi Shaybah

Hazrat Qatadah (may Allah have mercy on him) narrates that Hazrat Ali (may Allah be pleased with him) was asked about a mukatab slave who had been captured by the enemy, and then a man from among the Muslims bought him. What is the ruling regarding him now? He (may Allah be pleased with him) replied: If his master wishes, he can ransom him by giving him as collateral, and then this slave will remain with his master in such a way that he will pay the remaining amount of his contract of manumission. And the master will receive the slave’s wala (right of inheritance). And if he does not wish to do so, then the slave will remain with the buyer in the same condition.