Swearing that his wife will be unlawful for him if her mother sleeps in his bed

Q: One year ago, my wife and children stayed in Egypt after leaving the Kingdom. My wife invited her mother to stay with her in my house as the latter lives alone after her only son left Egypt. Although the house has many rooms, I knew that my mother-in-law sleeps with my wife in my bed. I asked my wife not to let her mother sleep in my bed as I was upset with her. When my wife seemed hesitant about it, and in a fit of anger, I took an oath that my wife will be unlawful for me if she let her mother sleep in my bed. Two weeks ago, my mother-in-law, who is staying with her son now, visited us. Unaware of the oath, she slept in my bed without my wife's knowledge. (Part No. 20; Page No. 189) When my wife discovered that her mother slept in my bed for not more than five minutes, she quickly asked her to leave the bed after telling her about the oath.My question is: Has the divorce taken place as a result of this? It is noteworthy that my wife did not know that her mother slept in my bed and once she knew she asked her to leave my bed. What would be the ruling if my wife forgot the oath, let her mother sleep in my bed, and rectified the situation upon remembering?I hope Your Eminence will issue a Fatwa (legal opinion issued by a qualified Muslim scholar) in writing so that I can send it to my wife.

A: If the reality is as you mentioned, that your wife did not let her mother sleep in your bed, there is no harm on you. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.