((اللَّهُمَّ إِنِّي ظَلَمْتُ نَفْسِي ظُلْماً كَثِيراً، وَلاَ يَغْفِرُ الذُّنوبَ إِلاَّ أَنْتَ، فَاغْفِرْ لِي مَغْفِرَةً مِنْ عِنْدِكَ وَارْحَمْنِي، إِنَّكَ أَنْتَ الغَفورُ الرَّحيمُ)).
O Allah, I have indeed oppressed my soul excessively and none can forgive sin except You, so forgive me a forgiveness from Yourself and have mercy upon me. Surely, You are The Most-Forgiving, The Most-Merciful. (From Yourself: i.e. from Your innermost grace without deserving it and a forgiveness which is befitting to your tremendous generosity.)
Al-Bukhari 8/168, Muslim 4/2078.