Dear Br. K. As-salaamu alaykum. You should pay a Kaffarah because you swore by something great and didnt keep up your promise. The Kaffarah is to provide a full meal for ten people in need or who are poor. You may give them the equivalent of the meal in terms of money until you reach ten people. If you are not financially able to do so, then you may fast three days. The fasting doesnt have to be three days in a row. Just a side note, even if you pay your kaffarah, try your best to quit smoking, it is really bad for your health and for other people around you. Good luck. Thank you for asking and God knows best.
(Source: IslamiCity) Classified in Kaffarah >