Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Makharraq that Hazrat Ali (may Allah be pleased with him) sent Hazrat Muhammad bin Abu Bakr (may Allah be pleased with him) to Egypt. He wrote a letter to him from Egypt and inquired about a mukatab (contracted slave) who dies leaving behind wealth and children. He (may Allah be pleased with him) wrote to him regarding the mukatab: If he dies leaving wealth for the payment of his contract, his master should be called and the amount due for the contract should be fully paid to him. Whatever remains after that will be inherited by his children.