Congressional Oath of Office
Article VI, Clause 3 of the United States Constitution states: "The Senators and Representatives.... shall be bound by Oath or Affirmation, to support this Constitution."
Pursuant to this constitutional provision, Congress enacted 5 U.S.C. 3331 which states:
"An individual, except the President, elected or appointed to an office of honor or profit in the civil service or uniformed services, shall take the following oath: "'I, AB, do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office of which I am about to enter. So help me God.'"