Is expiation obligatory for one who made a vow then forgot it, and is his forgetting considered negligence?

If someone forgets an oath (nadhr) and is unable to recall it, then according to the majority of scholars, they must offer an expiation for a broken oath (kaffarat yamin). Forgetting an oath is not considered negligence, as forgetfulness is fundamentally excused, based on the Prophet's (peace be upon him) saying: "Indeed, Allah has pardoned for my Ummah their mistakes and forgetfulness," and on the Almighty's saying: "{Our Lord, do not impose blame upon us if we have forgotten or erred}."