Zayd bin Aslam (may Allah have mercy on him) says that al-Qasim (may Allah have mercy on him) was asked about the divorces of a slave woman. He said: Her divorces are two and her waiting period is two menstrual cycles. When he was asked: Has anything reached you about this from the Prophet (peace and blessings be upon him)? He said: No.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرجعة / 15173