What is the ruling regarding a man who swore to his wife that she is "forbidden to him until the Day of Judgment" if she speaks to any non-mahram man, then she speaks to a non-mahram man, having forgotten the oath? And what is the ruling if she remembered the oath?

The questioner should fear Allah and repent to Him with sincere repentance. She should persist in doing what helps her in this regard, such as acquiring beneficial knowledge, performing righteous deeds, and associating with righteous women. She should beware of her conduct, which may lead her to indecency. Allah Almighty says: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins indecency and wrongdoing."

If the husband intended divorce by his saying "haram (definition)," then if the wife spoke to someone in a way that the husband dislikes, the divorce takes effect. However, if the wife was forgetful, then according to the Shafi'i school, the divorce does not take effect. There is no harm in adopting this opinion to alleviate hardship.