Hazrat Saeed bin Musayyib (may Allah have mercy on him) said: "If a slave marries with the permission of his master, then he is sold, his marriage will remain intact. But if someone marries off his slave-girl and then sells her, the selling of the slave-girl was considered her divorce."
Hadith Referenceسنن سعید بن منصور / كتاب الطلاق / 3121
Hadith Takhrij«أخرجه سعيد بن منصور فى «سننه» ترقيم الدرالسلفية برقم:، 1944، 1945، وعبد الرزاق فى «مصنفه» برقم: 13171»