Sahih Muslim 1349
صحيح مسلم#1349SahihKa'b b. 'Ujra reported Allah's Messenger (ﷺ) as saying:There are certain ejaculations, the repeaters of which or the performers of which after every prescribed prayer will never be caused disappointment:" Glory be to Allah" thirty-three times." Praise be to Allah" thirty-three times, and" Allah is most Great" thirty-four times
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 5:186