(705 ILCS 5/6) (from Ch. 37, par. 11)

Sec. 6.

The several judges of the supreme court, before entering upon the
duties of their office, shall take and subscribe the following oath or
affirmation:

I do solemnly swear (or affirm, as the case may be) that I will support
the constitution of the United States and the constitution of the state of
Illinois, and that I will faithfully discharge the duties of the office of
judge of the supreme court of the state of Illinois, according to the best
of my ability.

Which oath or affirmation may be administered by any person authorized
to administer oaths--a certificate whereof shall be affixed thereto by the
person administering the oath. And the oath or affirmation so certified
shall be filed in the office of the Secretary of State.

(Source: R.S. 1874, p. 327.)