Article 6 of the US Constitution requires the members of both houses of Congress to "be bound by their oath" to support the Constitution. The exact words in the last paragraph of Article 6 in the US Constitution are as follows:

"The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States".