Narrated Abu Huraira: The Prophet said, "It is not lawful for a woman (at the time of wedding) to ask for the divorce of her sister (i.e. the other wife of her would-be husband) in order to have everything for herself, for she will take only what has been written for her."

Narrated Abu Huraira: Allah's Apostle forbade the selling of things by a town dweller on behalf of a desert dweller; and similarly Najsh was forbidden. And one should not urge somebody to return the goods to the seller so as to sell him his own goods; nor should one demand the hand of a girl who has already been engaged to someone else; and a woman should not try to cause some other woman to be divorced in order to take her place.

Narrated Abu Huraira: Allah's Apostle said, "No woman should ask for the divorce of her sister (Muslim) so as to take her place, but she should marry the man (without compelling him to divorce his other wife), for she will have nothing but what Allah has written for her."