Chapter XXI: Section VI

I. 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 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.

II. No senator or representative shall, during the time for which he
was elected, be appointed to any civil office under the authority of
the United States, which shall have been created, or the emoluments
whereof shall have been increased during such time; and no person,
holding any office under the United States, shall be a member of
either house during his continuance in office.