Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Abdullah bin Rifaa that a person was told, "You intend to sell such-and-such slave-girl." That person said: "If I sell her, then she is free." Hazrat Abdullah thought that Hazrat Saeed bin Al-Musayyib was asked about this. He said: "In any case, I do not see any harm in it." And Hazrat Umar bin Abdul Aziz used to prohibit this.