RCW 36.16.040: Oath of office.

Every person elected to county office shall before he or she enters upon the duties of his or her office take and subscribe an oath or affirmation that he or she will faithfully and impartially discharge the duties of his or her office to the best of his or her ability. This oath, or affirmation, shall be administered and certified by an officer authorized to administer oaths, without charge therefor.