Is expiation (kaffarah) obligatory for someone who lit a cigarette but did not smoke it, after having sworn not to return to smoking?

The oath is based on the intention of the swearer. If he intends by his oath something that it can bear, his oath is directed to that, whether what he intended matches the apparent wording or contradicts it. If what the questioner did is not included in his oath, then he has not broken it. Otherwise, he is liable for an expiation for breaking an oath. It must be noted that assisting in smoking is forbidden, so the questioner must repent and not return to such a matter.