Question:
If a man marries a second wife, does he need to seek permission from the first wife?
Answer: حامدا ومصليا ومسلما
It is not necessary to seek permission from the first wife to marry a second wife, however it is necessary to be just and deal equitably in fulfilling the rights of both wives after marriage.
And Allah Ta’ala knows best.
(Hazrat Mufti) Ahmed Khanpuri (May Allah preserve him)
Mahoodul Fatawa 5/324