Sahih al-Bukhari
Oneness, Uniqueness of Allah (Tawheed) — Hadith #7563
كَلِمَتَانِ حَبِيبَتَانِ إِلَى الرَّحْمَنِ، خَفِيفَتَانِ عَلَى اللِّسَانِ، ثَقِيلَتَانِ فِي الْمِيزَانِ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ، سُبْحَانَ اللَّهِ الْعَظِيمِ "
The chain (isnad) appears to be missing from this record. Under review.
The Prophet (ﷺ) 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 6682).
كَلِمَتَانِ حَبِيبَتَانِ إِلَى الرَّحْمَنِ، خَفِيفَتَانِ عَلَى اللِّسَانِ، ثَقِيلَتَانِ فِي الْمِيزَانِ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ، سُبْحَانَ اللَّهِ الْعَظِيمِ "
See also hadith 6682.