Should the wife return to the heirs the money she took from her deceased husband's wealth without his knowledge, especially since it was to pay off a debt she owed and the inheritance has not yet been divided?

It is not permissible for a woman to take anything from her husband's money without his permission, unless he falls short in providing the obligatory maintenance. In that case, she may take what is sufficient for her and her child in a reasonable manner.

As for whoever takes something without permission and without a legitimate justification, she must repent and return the money to her husband, or seek forgiveness from him or from his heirs if he has passed away, because the Prophet, peace and blessings be upon him, said: "The hand is responsible for what it takes until it returns it," and he said: "Whoever has wronged his brother concerning his honor or anything else, let him seek his forgiveness today before there will be no dinar or dirham."

Therefore, the woman must return the amount she took to the deceased's estate so that it may be distributed according to Islamic law.