Each justice or judge of the United States shall take the following oath or affirmation before performing the duties of this office: ''I, _ _ _ _ _ _, do solemnly swear (or affirm) that I will administer justice without respect to persons, and do equal right to the poor and to the rich, and that I will faithfully and impartially discharge and perform all the duties incumbent upon me as _ _ _ under the Constitution and laws of the United States. So help me God.'