Sahih Muslim 1843
صحيح مسلم#1843SahihIbn Mas'ud reported Allah's Messenger (ﷺ) as saying:Wretched is the man who says: I forgot such and such a sura, or I forget such and such a verse, but he has been made to forget
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: 6:271