What is the ruling on the husband saying, "By all that is unlawful to me" as an oath concerning something he did not do, while he is truthful, and the wife saying, "Divorce be upon me" in jest?

Whoever does not break their oath made by uttering "haram" (unlawful) or "talaq" (divorce) has nothing to worry about regarding their marital bond. However, swearing by anything other than the name of Allah or His attributes is forbidden in Islam, as the Prophet, peace and blessings be upon him, said: "Whoever has to swear, let him swear by Allah or keep silent."

As for a woman swearing by divorce, no consequences follow from it, because divorce is in the hand of the husband. A Muslim should avoid swearing by "haram" or "talaq," for the fundamental principle is that an oath should be sworn by Allah or by His names and attributes.