Sahih Bukhari Volume 8, Book 75, Hadith Number 357.

Narated By Ibn ‘Abbas : Allah’s Apostle used to say at a time of distress, “La ilaha illal-lahu Rabbul-l-‘arsh il-‘azim, La ilaha illallahu Rabbu-s-samawati wa Rabbu-l-ard, Rabbu-l-‘arsh-il-Karim.”