Okla. Stat. tit. 51, § 64

Before the Senate shall proceed to consider the articles of impeachment, it shall organize itself into a court of impeachment, as provided herein, and every Senator present shall take the following oath or affirmation: "I do solemnly swear (or affirm) that I will faithfully and impartially try the impeachment against A. B., and do justice according to the law and the evidence."