Appointment of Chief Justice of Nigeria and Justices of the Supreme Court
Section 231(4) · 1999 Constitution (2004 edition)
What Constitution says
(4) If the office of Chief Justice of Nigeria is vacant or if the person holding the office is for any reason unable to perform the functions of the office, then until a person has been appointed to and has assumed the functions of that office, or until the person holding has resumed those functions, the President shall appoint the most senior Justice of the Supreme Court to perform those functions.
This is the 1999 Constitution as published in 2004. Later amendments aren't included yet, so a section may have changed since.
Original source
Official Gazette · CFRN 1999 official PDF · printed page 101. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections