Musannaf Ibn Abi Shayba 9:1434

17337. Umar ibn Harun narrated to us, from Ibn Jurayj, from Ibn Tawus, from his father, regarding a man who married a woman, and then it turned out that she was his sister through breastfeeding, and he had intercourse with her without knowing it. He said: They are to be separated, and she does not get the entire dowry; she gets some of it.