What is the Shar'i ruling on the second marriage remaining with the first wife's insistence on divorce, and what is your Shar'i guidance to the first wife to accept the second wife?

A man marrying four women is permissible, and there is no harm in it for the first wife. It is advised to keep the second wife, and to treat her and the first wife justly and kindly. The husband should advise the first wife and remind her that requesting the divorce of her co-wife is not permissible শর’আ (religiously), based on the hadith: "A woman should not ask for the divorce of her sister [in faith] to empty what is in her vessel."