Interesting the House doesn’t take an oath for Impeachment where the Senate does for the Trial....very interesting.
It's in the Constitution. Article I Section 3:
The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.-PJ
Articles of Impeachment are purely political in nature, for cause or not. Therefore no oath is required of the Representatives. However, the Senate “trial,” presided over by the Chief Justice follow the most basic rules of the USSC and therefore an oath is required.
Don’t know if that is correct, but it is MHO.