Sahih Muslim 1344
صحيح مسلم#1344SahihAbu Zubair reported:Abdullah b Zubair used to say La ilaha il-Allah at the end of every prayer like the hadith narrated by Ibn Numair and he reported it in the end, and then reported Ibn Zubair saying: The Messenger of Allah (ﷺ) uttered La ilaha il-Allah at the end of every prayer
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: 5:181