From Sahih Bukhari (Hadith 6682):
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "(The following are) two words (sentences or utterances) that are very easy for the tongue to say, and very heavy in the balance (of reward), and most beloved to the Gracious Almighty (And they are): Subhan Allahi wa bi-hamdihi; Subhan Allahi-l-'Adhim
Reference: Bukhari 6682