Musannaf Ibn Abi Shayba 9:568

Ibn Mahdi narrated to us, from Harb ibn Shaddad, from Yahya ibn Abi Kathir, who said: Ibn al-Najashi, the freed slave of Rafi‘ ibn Khadij, narrated to us that Rafi‘ ibn Khadij married a woman alongside his wife. He said to his first wife, "If you wish, I will keep you, but I will not divide [my time] for you, and if you wish, I will divorce you." She chose for him to keep her and not divorce her.