Do what I swore by constitute a Ghamus oath or necessitate expiation, given that there were exceptional circumstances in which I did not intend to lie?

We thank the questioner for her attempt to avoid the bad and forbidden habit of shaking hands with men, and she should continue in that. The mentioned oath is not an oath that dips one in sin (yameen ghamus), but rather it is among the vain oaths (laghw al-yameen) for which there is no expiation (kaffarah); because the questioner had forgotten the exceptional cases in which she shook hands, and she did not intentionally lie in her oath. There is no expiation for one who swore an oath believing it to be true, only for it to turn out otherwise, for the yameen ghamus is that which a person swears falsely and knowingly. However, if the oath was that she would not shake hands with men immediately or in the future, then the oath would be binding and she would break it by shaking hands with any man, unless she had an intention to specify certain men.