Article 1, Section 6, Clause 1

The Senators and Representatives shall receive a Compensation for their Services, to be ascertained by Law, and paid out of the Treasury of the United States. They shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place.

1.Bill of Rights, sec. 9, 2, 16 Dec. 1689
2.Holiday v. Pitt
3.William Blackstone, Commentaries 1:159--61, 1765
4.Thomas Jefferson, Bill for Giving the Members of the General Assembly an Adequate Allowance, 12 Dec. 1778
5.Articles of Confederation, art. 5, 1 Mar. 1781
6.John Adams to John Jebb, 21 Aug. 1785
7.Records of the Federal Convention
8.Vermont Constitution of 1786, CH. 1, ART. 16
9.A Georgian, 15 Nov. 1787
10.Cornelius, 11--18 Dec. 1787
11.Debate in Massachusetts Ratifying Convention, 19 Jan. 1788
12.Luther Martin, Genuine Information, 1788
13.Bolton v. Martin
14.Geyer's Lessee v. Irwin
15.James Madison, Militia Bill, House of Representatives, 16 Dec. 1790
16.James Wilson, Legislative Department, Lectures on Law, 1791
17.House of Representatives, Reduction of Salaries, 27 Jan. 1795
18.Thomas Jefferson (AND James Madison), Protest to the Virginia House of Delegates, 1797
19.Coxe v. McClenachan
20.Kentucky Constitution of 1799, ART. 2, SEC. 24
21.Charles Pinckney, Breach of Privilege, Senate, 5 Mar. 1800
22.Coffin v. Coffin
23.Hurst's Case
24.Joseph Story, Commentaries on the Constitution 2:§§ 849--63, 1833