The Acceptance of the First Wife is Not a Condition For One Who Wishes to Marry Another
There is no doubt that Islaam has permitted plurality of wives, but is it required for the husband to seek the acceptance of his first wife before marrying the second one?
It is not obligatory for the husband, when he wishes to marry another, to get his first wife’s acceptance, but it is a noble trait of character and good relations for him to appease her by whatever decreases the pain which women naturally feel in such situations. This may be achieved by smiling, greeting her warmly and speaking kindly to her, and by whatever money you can afford, if her acceptance requires it.
Permanent Committee for Research and Verdicts
Fataawa Islamiyyah, Darussalam, volume 5, page 353