The Constitution mandates that: “When sitting for that purpose [trying impeachments] they [the Senate] shall be on oath or affirmation.” (See: Const., Art. I, Sect. 3, Clause 6) The oath that the Senate requires every senator to take before being allowed to participate in an impeachment trial demands that they “solemnly swear or affirm... in all things appertaining to the trial (to) do impartial justice according to the Constitution and law.” (Emphasis added) (See: Procedure and Guidelines for Impeachment Trials in the United States Senate, pp. 25-26 & p. 61)