Is expiation incumbent upon the swearer if the one for whom the oath was made did not hear him?

Swearing to prevent someone from doing something is a binding oath, and expiation becomes incumbent upon the one who swore the oath if he breaks it. If a person swears an oath upon another, and the one upon whom the oath was sworn does not comply, then expiation is incumbent upon the one who swore the oath, by agreement of the jurists. However, if the one upon whom the oath was sworn is someone who complies with the command of the one who swore the oath, and he performs the action sworn against, either out of ignorance or forgetfulness of the oath, then there is no expiation upon the one who swore the oath, because he is considered as if he did not break the oath.