Does a triple divorce take effect upon the husband if he rides a car shared by his wife and her brother, after he had sworn that he would not ride it due to a dispute that occurred between him and his wife's brother, and then they reconciled?

Conditional divorce occurs, according to the majority of scholars, upon the fulfillment of the condition. So, if the husband swore by triple divorce that he would not ride a car, the solution is for him not to ride it. If he rides it, triple divorce occurs according to the majority of scholars, and she becomes unlawful to him until she marries another husband.

This is unless the husband intended that he would not ride the car for a specific period or in a specific manner. In such a case, the oath is not broken if he rides it after that period or in a manner different from what he swore upon, just as an oath by circumstances (bisaat) is specific if the reason for it disappears without his action.

It appears here that there is no such specificity for either of them, because the husband's oath not to ride the car and not to set foot in it implies negating riding it in any manner, and his reconciliation with his brother negates the application of the circumstances (bisaat).

Shaykh al-Islam Ibn Taymiyyah and those who agreed with him hold that if the husband intended threat or prevention and did not intend divorce, only an expiation for an oath (kaffarat yameen) is due. If he intended divorce, then a single divorce occurs. The husband is advised to refer to the Sharia (definition) court or consult trustworthy scholars directly.