Ruling on keeping a slave woman in addition to four wives

Question:
A man has four wives and a slave woman, and the slave woman gave birth. Does he have to divorce one of them? And if he marries the slave woman and frees her, is it necessary that he divorce one of the four?

Answer:
He is not allowed more than four wives. If he has a slave woman, she is not counted among the wives. This is because Allah (Exalted and Majestic is He) said: [Surat al-Nisa: 3]. The number of slave women does not matter; the limit applies only to wives, meaning free women. He may have four or fewer free wives. Even if he has five or ten slave women in addition to them, it does not harm him. However, if he frees her, makes her freedom her mahr, and marries her, she must be one of the four; she cannot be a fifth. If he marries her as a fifth wife, the contract is invalid. He is not allowed more than four.