Hazrat Mujahid (may Allah have mercy on him) was asked whether zihar (a form of divorce) is valid with a slave woman. He considered it nothing (i.e., not valid). I said: "Allah the Exalted says: «الَّذِينَيُظَاهِرُونَمِنْنِسَائِهِمْ» Is she not included among women?" He replied: "Allah said: «وَاسْتَشْهِدُواشَهِيدَيْنِمِنْرِجَالِكُمْ» So are slaves not men? Then is the testimony of slaves permissible?"
Hadith Referenceسنن سعید بن منصور / كتاب الطلاق / 3030
Hadith Takhrij«أخرجه سعيد بن منصور فى «سننه» ترقيم الدرالسلفية برقم:، 457، 1853، والبيهقي فى«سننه الكبير» برقم: 20675»