Musannaf Ibn Abi Shayba 9:347

16250. Abd al-A’la narrated to us, from al-Jurayri, from Abu Nadra, who said: A man came to Umar and said: "I have a slave woman and her daughter, and they have both pleased me, so may I have intercourse with them?" He (Umar) said: "A verse has permitted it, and a verse has forbidden it. As for me, I would not approach this."