Is the husband sinful for the money he took from his unjust sponsor without his knowledge, and is an expiation due for his oath, and what is his punishment?

If the husband has money with his guarantor, and he is unable to retrieve it without proof, then he takes from his guarantor's money without his knowledge, there is no sin upon him. This is called al-Dhafar (taking one's right by force) and is permissible under two conditions: that he does not take more than his due, and that he is safe from harm to himself. As for the oath, he must seek forgiveness, and there is no expiation required of him.