Du'a for forgiveness

اللَّهُمَّ إِنِّي أَسْأَلُكَ يَا اللَّهُ بِأَنَّكَ الْوَاحِدُ الْأَحَدُ الصَّمَدُ الَّذِي لَمۡ يَلِدۡ وَلَمۡ يُولَدۡ وَلَمۡ يَكُن لَّهُۥ كُفُوًا أَحَدُۢ أَنْ تَغْفِرَ لِي ذُنُوبِي إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمُ

Allahumma inni as'aluka ya Allahu bi'annakal-wahidul-ahadus-samadul-ladhi lam yalid wa lam yulad, wa lam yakun lahu kufuwan ahad an taghfira li dhunubi innaka antal-ghafurur-rahim

O Allah, I ask You, O Allah, by the fact that You are the One, the Unique, the Self-Sufficient Master, Who (is described thus): 'He begetteth not nor was begotten. And there is none comparable unto Him,' that You forgive me my sins; indeed You are the Forgiving, the Merciful.

Sunan al-Nasāʾī 1301