Is a man's marriage to his wife's sister permissible or forbidden after divorcing her sister, given that they both eloped and got married?

The act of adultery committed by the man and woman is one of the gravest evils. He is not permitted to marry his wife's sister as long as his wife is in her 'iddah (waiting period). Even if he divorces her with an irrevocable divorce, many scholars prohibit marrying her sister or a relative of hers while she is in her 'iddah. The reason for this negligence is turning away from Allah's law, which forbids seclusion with a woman who is not permissible for him. The Prophet (peace be upon him) said: "No man should be alone with a woman, and no woman should travel except with a mahram (unmarriageable kin)." This evil is a result of turning away from Allah's law. Allah Almighty has forbidden adultery and warned against it and its causes, such as seclusion, talking, and looking. People must return to their religion and apply its law.