What is the ruling on making a husband swear on the Qur'an that he will not marry again? And is a wife entitled to seek divorce if her husband marries another?

For a wife to make her husband swear not to marry another woman is not unlawful in Islamic law. However, he has the right to marry a second wife if he desires and is able to be just. If he marries, he has broken his oath, and an expiation for an oath becomes incumbent upon him. The wife does not have the right to demand a divorce without a legitimate religious reason if he marries. If she cannot be patient, dislikes her husband, and fears failing in her duties towards him, she may resort to Khul'. The husband should preserve his wife's kindness and not rush into marrying a second wife unless there is a compelling reason that outweighs the initial situation.