What is the expiation for not abiding by an oath of hearing and obedience that was previously sworn?

The questioner did not mention what he swore upon, nor what is meant by "hearing and obeying." However, if what is intended is to be present with those he swore to and to obey their commands, and then he ceased doing so, he must offer expiation for an oath. And if what he swore upon does not conform to the Sharia, he must break his oath.