Sahih Bukhari
Oneness, Uniqueness of Allah (Tawheed)
Volume: 009 / Book Number: 093 / Hadith Number: 652
Narrated Abu Huraira:
The Prophet said, "(There are) two words which are dear to the Beneficent (Allah) and very light (easy) for the tongue (to say), but very heavy in weight in the balance. They are: 'Subhan Allah wa-bi hamdihi' and 'Subhan Allah Al-'Azim." (See Hadith No. 673, Vol. 8).