once
اللَّهُمَّ إِنِّي ظَلَمْتُ نَفْسِي ظُلْماً كَثِيراً، وَلاَ يَغْفِرُ الذُّنوبَ إِلاَّ أَنْتَ، فَاغْفِرْ لِي مَغْفِرَةً مِنْ عِنْدِكَ وَارْحَمْنِي، إِنَّكَ أَنْتَ الغَفورُ الرَّحيمُ
Edition transliteration
Allahumma innee thalamtu nafsee thulman katheeran wala yaghfiruth-thunooba illa ant, faghfir lee maghfiratan min AAindik warhamnee, innaka antal-Ghafoorur-Raheem.
Meaning
(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.)
Source and references
Hisn al-Muslim, entry 57.The reference is copied from the edition; separate editorial verification is not complete yet.
Source edition: Fortress of the Muslim. Open source ↗