Sahih Muslim 1683
صحيح مسلم#1683SahihA'isha reported that the Messenger of Allah (ﷺ) used to observe two (supererogatory) rak'ahs in between the call to prayer and the Iqama of the dawn prayer
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: 6:113