Senate Rule III - Oaths

111th Congress
The oaths or affirmations required by the Constitution and prescribed by law shall be taken and subscribed by each Senator, in open Senate, before entering upon his duties.

OATH REQUIRED BY THE CONSTITUTION AND BY LAW TO BE TAKEN BY SENATORS

* "I, A__ B__, 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 on which I am about to enter: So help me God." (5 U.S.C. 3331.)

109th Congress
The oaths or affirmations required by the Constitution and prescribed by law shall be taken and subscribed by each Senator, in open Senate, before entering upon his duties.

OATH REQUIRED BY THE CONSTITUTION AND BY LAW TO BE TAKEN BY SENATORS
 * "I, A__ B__, 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 on which I am about to enter: So help me God." (5 U.S.C. 3331.)

Resources

 * Rules of the 109th U.S. Senate

Articles

 * "Rule III," U.S. Senate - Committee on Rules and Administration, 2005.