If a husband takes his wife back after explicitly divorcing her, do the two previous suspended divorces remain valid, such that if the sworn-upon event occurs in the future, another divorce would take place? And what is the ruling on a husband who frequently swears by divorce?

The majority of jurists hold that a contingent divorce takes effect if the condition it was contingent upon occurs. This is the fatwa that is acted upon, contrary to Ibn Taymiyyah, who holds that it does not take effect if the intention was to threaten, and that it can be resolved with an expiation for an oath (kaffarat yamin). The contingency remains even if he divorces her with an immediate divorce (less than three pronouncements), or if her 'iddah (waiting period) ends and he then remarries her. If the husband made the divorce contingent upon a characteristic, and then remarried her after an irrevocable divorce (baynunah), she will be divorced if that characteristic is found. For example, if someone says: "If you speak to your father, you are divorced," and then remarries her, and she speaks to her father, she will be divorced. However, if the husband intended to make the divorce contingent upon an action within a specific time, then the contingency is restricted to that time, because the intention of the one swearing an oath specifies the general and restricts the absolute. The husband is advised to avoid swearing by divorce.