Is it necessary to abstain from speaking for three days, or is fasting for three days sufficient as an expiation for a broken oath, and is the oath still valid or has it been nullified?

Whoever swears by Allah not to do something, then does it, has broken his oath and must offer expiation for the oath (kaffarat yamin). This expiation is feeding ten poor persons, or clothing them, or freeing a slave. If one cannot find any of these, then he must fast for three days. It is not permissible to resort to fasting except when unable to feed or clothe or free a slave. You are not required to refrain from permissible speech.