Sahih Muslim 1060
صحيح مسلم#1060SahihThabit reported it on the authority of Anas:While leading you in prayer I do not shorten anything in the prayer. I pray as I saw the Messenger of Allah (ﷺ) leading us. He (Thabit) said: Anas used to do that which I do not see you doing; when he lifted his head from bowing he stood up (so long) that one would say: He has forgotten (to baw down in prostration). And when he lifted his head from prostration, he stayed in that position, till someone would say: He has forgotten (to bow down in prostration for the second sajda)
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: 4:222