Is an expiatory offering (kaffarat yamin) required of one who swore not to speak to her mother-in-law on the telephone, but then speaks to her after another person has called the number?

If a woman speaks to her mother-in-law after swearing to stop speaking to her, then expiation (kaffara) becomes obligatory upon her. The fact that she obtained the number from someone else does not prevent the expiation from becoming obligatory, because her speaking to her mother-in-law has indeed occurred. However, if the mother-in-law stops harassing her, then the reason that prompted the oath has ceased to exist. In this case, no expiation is required if the breaking of the oath occurs after the reason has ceased.