What is the ruling on being lenient in swearing by divorce, whether falsely, in jest, or as a threat, and what is your guidance to Muslims to avoid that?

Threatening with divorce does not constitute a divorce. It is forbidden to swear by other than Allah, and the prohibition is even stronger against swearing by divorce, as it is among the oaths of the wicked. If a husband swears by divorce and intends for it to occur upon the fulfillment of what was sworn upon, then the divorce takes place. Similarly, divorce occurs if he only intended a threat, according to the majority of jurists. Ibn Taymiyyah, however, held that only an expiation for an oath is required if he intended a threat, prevention, or breaking the oath. Swearing by divorce to commit a forbidden act is a heinous and reprehensible evil, and the one sworn against must not obey someone who swears upon committing a forbidden act.