Swearing if any woman rides the car with him, his wife will be unlawful to him

Q 1: I had a dispute with my wife because she invited (Part No. 23; Page No. 164) one of her friends, who is a female teacher in her school, to ride the car with us. I do not feel comfortable with her friend. Therefore, when we returned home, the dispute escalated and I warned my wife against inviting any woman to ride the car with us. I told her, "I swear by Allah that if you invite so-and-so women to ride my car, it will be the last day I spend with you." I was trying to make my wife understand that I am angry with those two women and intended by my swearing to threaten her not to do this action again. It should be noted that my wife has not invited any woman to ride the car with us from that day due to my swearing, nor have I allowed any of them to ride the car. Is this considered an oath? If it is, what is the Kaffarah (expiation) for breaking it? Will my wife incur anything if she invites any woman to ride the car with us? Please, advise. May Allah reward you with the best!

A: This is an oath that you must fulfill by preventing these women from riding the car with you. If you break this oath, you must offer a Kaffarah, which is feeding ten Miskins (needy people) of the staple foodstuff; each with half a Sa` (1 Sa`=3 kg. Approx.) of wheat or sufficient cooked food, or clothing them or freeing of a believing slave. If you cannot afford any of these alternatives, you must fast for three days. (Part No. 23; Page No. 165) May Allah grant us success. May blessings and peace be upon our Prophet Muhammad, his family and Companions!