What is the ruling on someone who swore an oath to abstain from a specific act for the rest of his life, then changed his intention to several months while in a state of intense anger, and is expiation (kaffarah) obligatory upon him?

A Muslim should not swear excessively by Allah, as this leads to hardship and breaking oaths, and shows a lack of reverence for Allah. It is a form of audacity towards Him. Allah the Almighty says: "And do not make [your oath by] Allah an obstacle to your doing good" and "And guard your oaths."

The aforementioned oath is a righteous oath for which there is no expiation unless what was sworn upon is done. However, if it involves sin, or cutting off ties of kinship, or if something else is better than it, then the swearer must release himself from it by expiation for an oath and doing what he swore to abandon, due to the Prophet's (peace be upon him) saying: "If you swear an oath, and then you see that something else is better than it, then do that which is better and make expiation for your oath."

The expiation for an oath is to feed ten poor persons from the average of what one feeds his family, or to clothe them, or to free a slave. If one cannot find [means], then fast for three days. The phrase "then after several seconds" is not considered an exception and does not nullify the oath because it is merely a change of intention.