"Besides, carnal connexion is the right of a free woman for the gratifying of her passion, and the propagation of children (whence it is that a wife is at liberty to reject a husband who is an eunuch or impotent); whereas a slave possesses no such right.—A man, therefore, is not at liberty to injure the right of his wife, whereas a master is absolute with respect to his slave. If, also, a man should marry the female slave of another, he must not perform the act of Azil with her without the consent of her master."
January 1, 1970
https://en.wikiquote.org/wiki/Islamic_views_on_concubinage