Sahih Muslim 1691
صحيح مسلم#1691SahihIbn 'Abbas reported that the Messenger of Allah (ﷺ) used to recite in first of the two (supererogatory) rak'ahs of the dawn:"Say: We believed in Allah and what was revealed to us..." verse 136 from Surah Baqara, and in the second of the two: "I believe in Allah and I bear testimony that we are Muslims" (iii)
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: 6:121