Muhammad bin Muslim bin Tadras محمد بن مسلم بن تدرس أبو الزبير · The Chapters on Manumission (of Slaves)

“Whoever becomes the master of a Mahram relative (with whom marriage is not lawful), he becomes free.”

`Aishah had a male slave and a female slave who were married. She said: “O Messenger of Allah (ﷺ), I want to free them both.” The Messenger of Allah (ﷺ) said: “If you free them, then start with the man before the woman.”