I vowed to fast for three days, but I didn't fast until Ramadan arrived. What should I do?

If you vowed to fast specific days and did not fast them, you must make them up and offer expiation, regardless of whether the delay was due to an excuse or not. However, if you vowed to fast unspecified days, you must hasten to fast them, and there is no expiation due for delaying them before Ramadan. The expiation for a vow is the same as the expiation for an oath: either freeing a slave, or feeding ten needy persons, or clothing them. If one cannot find these, then one must fast three days.