Is expiation (kaffarah) by fasting three days obligatory upon one who swore unintentionally by inviting a woman, not intending the oath but rather a mere courtesy, and he does not wish to invite her?

An oath uttered inadvertently, without intention, is considered a vain oath (laghw), and there is no expiation for it, based on the Almighty's saying: "Allah will not impose blame upon you for what is unintentional in your oaths." This applies to the questioner's oath. It is advised to visit the woman and invite her, counseling her gently regarding the hijab, in order to clear one's conscience, to uphold the good reputation of veiled women, and to fulfill the duty of offering sincere advice.