Declaration of assets and liabilities; oaths of President
Section 140 · 1999 Constitution (2004 edition)
What Constitution says
(1) A person elected to the office of President shall not begin to perform the functions of that office until he has declared his assets and liabilities as prescribed in this Constitution and he has taken and subscribed the Oath of Allegiance and the oath of office prescribed in the Seventh Schedule to this Constitution. (2) The oaths aforesaid shall be administered by the Chief Justice of Nigeria or the person for the time being appointed to exercise the functions of that office.
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 71. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections