The leading duʿāʿ for seeking forgiveness (istighfār)
from the Prophet ﷺ who said: "If anyone says in the morning or in the evening: 'O Allah! You are my Lord; there is no god except You, You have created me, and I am Your servant and I hold on to Your covenant and promise as much as I can; I seek refuge in You from the evil of what I have done: I acknowledge Your favour upon me, and I acknowledge my sin. So pardon me, for none but You pardons sins,' and he dies during the daytime or during the night, he will enter Paradise."
عَنِ النَّبِيِّ ﷺ قَالَ: «مَنْ قَالَ حِينَ يُصْبِحُ أَوْ حِينَ يُمْسِي: (اللَّهُمَّ أَنْتَ رَبِّي لاَ إِلَهَ إِلاَّ أَنْتَ، خَلَقْتَنِي وَأَنَا عَبْدُكَ وَأَنَا عَلَى عَهْدِكَ وَوَعْدِكَ مَا اسْتَطَعْتُ، أَعُوذُ بِكَ مِنْ شَرِّ مَا صَنَعْتُ، أَبُوءُ بِنِعْمَتِكَ وَأَبُوءُ بِذَنْبِي، فَاغْفِرْ لِي إِنَّهُ لاَ يَغْفِرُ الذُّنُوبَ إِلاَّ أَنْتَ) فَمَاتَ مِنْ يَوْمِهِ أَوْ مِنْ لَيْلَتِهِ دَخَلَ الْجَنَّةَ۔»