Sahih Al Bukhari – Book of Invocations
Volumn 008, Book 075, Hadith Number 415.
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Narated By Abu Huraira : The Prophet said, "There are two expressions which are very easy for the tongue to say, but they are very heavy in the balance and are very dear to The Beneficent (Allah), and they are, 'Subhan Allah Al-'Azim and 'Subhan Allah wa bihamdihi.'"