Yahya related to me from Malik that he heard Rabia ibn Abd ar-Rahman say that a slave could marry four women.Malik said,"This is the best of what I have heard about the matter."Malik said, "The slave differs with the muhallil if the slave is givenpermission by his master for his ex-wife. If his master does not givehim permission, he separates them. The muhallil is separated in anycase if he intends to make the woman halal by marriage."Malik said, "When a slave is owned by his wife or a husband owns hiswife, the possession of each of them is rendered void without divorce.If a man, for instance, is married to a slave-girl, and then he buysher, he must divorce her as a matter of course. They can then re-marry. If they re-marry afterwards, that separation was not divorce."Malik said, "When a slave is freed by his wife who owns himand she is in the idda-period from him, they can only return to eachother after she has made another marriage."
USC-MSA web (English) reference: Book 28, Hadith 43
Arabic reference: Book 28, Hadith 1138