Sahih Muslim 373
صحيح مسلم#373SahihIt is narrated on the authority of Ibn 'Umar ('Abdullah b. 'Umar) that the Messenger of Allah (ﷺ) observed:Verily Islam started as something strange and it would again revert (to its old position) of being strange just as it started, and it would recede between the two mosques just as the serpent crawls back into its hole
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: 1:280