Sahih Muslim 484 d
'A'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."
حَدَّثَنِي مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنِي عَبْدُ الأَعْلَى، حَدَّثَنَا دَاوُدُ، عَنْ عَامِرٍ، عَنْ مَسْرُوقٍ، عَنْ عَائِشَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُكْثِرُ مِنْ قَوْلِ ‏"‏ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ أَسْتَغْفِرُ اللَّهَ وَأَتُوبُ إِلَيْهِ ‏"‏ ‏.‏ قَالَتْ فَقُلْتُ يَا رَسُولَ اللَّهِ أَرَاكَ تُكْثِرُ مِنْ قَوْلِ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ أَسْتَغْفِرُ اللَّهَ وَأَتُوبُ إِلَيْهِ ‏.‏ فَقَالَ ‏"‏ خَبَّرَنِي رَبِّي أَنِّي سَأَرَى عَلاَمَةً فِي أُمَّتِي فَإِذَا رَأَيْتُهَا أَكْثَرْتُ مِنْ قَوْلِ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ أَسْتَغْفِرُ اللَّهَ وَأَتُوبُ إِلَيْهِ ‏.‏ فَقَدْ رَأَيْتُهَا ‏{‏ إِذَا جَاءَ نَصْرُ اللَّهِ وَالْفَتْحُ‏}‏ فَتْحُ مَكَّةَ ‏{‏ وَرَأَيْتَ النَّاسَ يَدْخُلُونَ فِي دِينِ اللَّهِ أَفْوَاجًا * فَسَبِّحْ بِحَمْدِ رَبِّكَ وَاسْتَغْفِرْهُ إِنَّهُ كَانَ تَوَّابًا‏}‏ ‏"‏ ‏.‏