Am I sinful if I prevent my husband from marrying another woman, even though I do not desire divorce, or would separation be better if this matter affects my religious commitment?

The Shari'ah has permitted a man to marry more than one woman as long as he is able to be just, and it is not permissible for a woman to prevent her husband from doing so. A wife's beautification and good companionship are religiously مطلوب, and this may make the husband dispense with marrying another. A husband's marriage to a second wife is not a legitimate excuse for seeking divorce unless the wife is severely harmed. A wife should not rush to seek divorce. It is possible to maintain commitment by associating with Quran memorization centers and knowledge lessons, and by keeping company with righteous women. Polygyny was legislated by Allah for many reasons.