Is the one who breaks an oath required to offer expiation for that oath if the breaking of it was an act of disobedience, such as one who swore not to commit a sin and then fell into it? And is this type of oath considered legislated or an innovation?

Whoever swears an oath to abandon a sin is forbidden from breaking their oath, because breaking it would lead them into what is unlawful. Should they break their oath, they are obliged to repent and offer expiation for the oath. Scholars have differed on the ruling of swearing an oath to abandon sins, with some considering it recommended and others not. It is better for a Muslim not to swear an oath to abandon a sin unless they believe it will help them avoid it, while it is obligatory to uphold the oath.