Sahih al-Bukhari 821
صحيح البخاري#821SahihNarrated Thabit:Anas said, "I will leave no stone unturned in making you offer the prayer as I have seen the Prophet (ﷺ) making us offer it." Anas used to do a thing which I have not seen you doing. He used to stand after the bowing for such a long time that one would think that he had forgotten (the prostrations) and he used to sit in-between the prostrations so long that one would think that he had forgotten the second prostration
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 10:215