Does swearing not to deliver due to cold, and then delivering despite the oath, necessitate expiation or is it considered a thoughtless oath (laghw al-yameen)?

If a person swears an oath upon another over whom he has no authority not to do something, and that person then does it, the one who swore the oath is bound by an expiation for a broken oath, absolutely, whether the one sworn upon did so intentionally, forgetfully, or ignorantly.

However, if the oath was uttered unintentionally, it falls under the category of a 'vain oath' (laghw al-yameen), for which no expiation is required.