Is it obligatory to remind a person who has erred that there is an expiation for an oath (kaffarat yamin) due upon him if he has forgotten, and does the ruling differ based on his level of religious commitment or the frequency of his oaths?

It is prescribed to remind someone who has forgotten their oath so that they may fulfill it or perform the necessary expiation. Reminding them is obligatory because it falls under giving advice (naseehah) and enjoining good. Scholars have stated that "religion is naseehah," and they have mentioned branches concerning the obligation of informing those who have forgotten, such as informing someone who intends to eat or drink in Ramadan out of forgetfulness or ignorance, or informing someone who knows that water is impure when an ignorant person intends to use it, or waking up a sleeping person for prayer if the time is short. There is no difference between someone who frequently swears oaths and someone who does not. For those for whom expiation by feeding or clothing is not obligatory, they expiate by fasting. It is important to note that if someone swears an oath to do something, they are not obligated to fulfill their oath unless it is to perform an obligation or avoid a prohibition. If someone swears an oath to perform a disliked act or omit a recommended one, it is sunnah for them to break their oath. If someone swears an oath to perform a recommended act or omit a disliked one, it is disliked for them to break their oath. If someone swears an oath to perform an obligation or omit a prohibition, it is forbidden for them to break their oath. If someone swears an oath to perform a prohibited act or omit an obligation, it is obligatory for them to break their oath. If someone swears an oath concerning a permissible matter, they have the choice between breaking it or fulfilling it, and fulfilling it is more virtuous.