Musannaf Ibn Abi Shayba 9:1646

Abu Bakr narrated to us, he said: Abbad ibn al-Awwam narrated to us, from Ghalib, who said: I asked al-Hasan—or he was asked—about a man who has two wives in one house. He said: They used to dislike the *wajs*, which is that he has intercourse with one of them while the other is looking or listening.