What is the ruling on swearing to do something and then not doing it? Is expiation for an oath (kaffarat yameen) required?

Excessive swearing is not befitting a Muslim. Whoever takes a remunerative oath and then breaks it, expiation becomes obligatory upon them. The majority of jurists stipulate remembrance for expiation to be binding upon breaking an oath. So, if the sworn-upon act is performed out of forgetfulness, the oath is not broken, and there is no expiation for it, according to the more preponderant and well-known opinion. And she must repent to Allah and abandon the habit of swearing excessively.