For thou saidst What advantage will it be unto thee? i.e. What advantage will thy righteousness be unto thee? Job had certainly argued that his righteousness brought him no temporal advantage; but he had always a conviction that he would ultimately be the better for it.
Elihu, however, does not acknowledge this; and, assuming that Job expects to receive no advantage at all from his integrity, argues that God is not bound to afford him any. And, What profit shall I have, if I be cleansed from my sin?
rather, And what profit shall f have, more than if I had sinned? (see the Revised Version, and compare the comments of Rosenmuller and Canon Cook).