It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) would often recite «سُبْحَنَكَرَبَّنَاوَبِحَمْدِكَاَللّٰهُمَّاغْفِرْلِيْ», and when Surah Nasr was revealed to the Prophet (peace and blessings be upon him), he began to say: «سُبْحَانَكَرَبَّنَاوَبِحَمْدِكَاللّٰهُمَّاغْفِرْلِيإِنَّكَأَنْتَالتَّوَّابُالرَّحِيمُ» "O Allah! Forgive me, for You are indeed the Acceptor of repentance, the Most Merciful."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 3719
Hadith Gradingحکم دارالسلام:حسن لغيره، وهذا إسناد ضعيف لانقطاعه، أبو عبيدة لم يسمع من عبدالله.