clean as a hound's tooth

Rogers left the Department of State in September, 1973, before the Watergate scandal had implicated Nixon and some of his principal White House aides. He couldn't have picked a better time to return to private life and all his friends were happy for him. Bill Rogers simply cleaned his desk and moved back to his old law firm, Rogers and Wells. He came through all this untarnished, as clean as a hound's tooth.