If a person swore, "By Allah, I will not commit this sin for the rest of my life," then broke their oath, violated it, and offered expiation, is expiation obligatory every time they commit the same sin?

Whoever resolves to abandon a sin should seek Allah's help, firmly intend sincere repentance, and utilize the assisting means. However, they should not use oaths as a method to achieve its abandonment. If one swears an oath to abandon something unlawful, they are obligated to uphold their oath, and it is not permissible for them to unilaterally release themselves from it. If they commit the sin they swore to abandon in the future and offer expiation for their oath, they have then released themselves from that oath. If they commit the act again, there is no further expiation due, but they must repent and firmly resolve not to return to that sin. A binding oath concerning the future necessitates expiation upon its breach. The phrase "for the rest of my life" does not imply repeated expiation with repeated breaches; rather, it signifies an emphasis on the resolve not to breach the oath. The oath dissolves and becomes void with the first transgression, unlike a prohibition, which remains continuous, and sin is reiterated with its repetition.