What is the ruling on one who swears oaths such as: "By God Almighty, this is the last time," or "My wife is unlawful to me if this is not the last time," to prevent himself from repeating ablution due to obsessive-compulsive disorder, and then repeats the ablution after these oaths?

The answer regarding obsessive thoughts and doubts about ablution can be summarized as follows:

1. If you swear by "By Allah the Almighty, this is the last time," and then repeat ablution, you are liable for an expiation for breaking an oath (kaffarat yamin). 2. Your statement: "All girls are forbidden to me if this is not the last time." If you intended divorce, then nothing is incumbent upon you, as divorce does not occur before marriage. If you intended zhihar (analogous to comparing one's wife to an unmarriageable relative), the majority of scholars consider it to be binding. However, the Shafi'is hold that zhihar concerning a non-mahram woman is not valid. If you intended an oath by Allah or intended nothing specific, you are liable for an expiation for breaking an oath. 3. Your statement: "My wife is forbidden to me if this is not the last time," while you are not married, falls under the same ruling regarding prohibition as mentioned above. If an oath of zhihar is repeated, one expiation is sufficient. 4. Your statement: "My mother and sister are forbidden to me if this is not the last time," does not require any expiation, nor is anything incumbent upon you, because they are already permanently forbidden (mahram).

You must strive against your inner self to distance yourself from obsessive thoughts, disregard them, and frequently supplicate to Allah.