Sahih Muslim 1088
صحيح مسلم#1088SahihA'isha reported:The Messenger of Allah (ﷺ) recited often these words: Hallowed be Allah and with His praise, I seek the forgiveness of Allah and return to Him. She said: I asked: Messenger of Allah, I see that you often repeat the saying" subhan allahi bihamdihi astag firullahi watubuilaih" whereupon he said: My Lord informed me that I would soon see a sign in my Ummah, so when I see it I often recite (these) words: Hallowed be Allah and with His Praise, I seek forgiveness of Allah and return to Him. Indeed I saw it (when this verse) was revealed:" When Allah's help and victory came, it marked the victory of Mecca, and you see people entering into Allah's religion in troops, celebrate the praise of Thy Lord and ask His forgiveness. Surely He is ever returning to Mercy
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: 4:250