Narrated Shaddad bin 'Aus:

The Prophet ﷺ said, "The most superior way of asking for forgiveness from Allah is: 'Allahumma anta Rabbi la ilaha illa anta. Khalaqtani wa ana 'abduka, wa ana 'ala 'ahdika wa Wa'dika mastata'tu abu'u Laka bi ni 'matika wa abu'u Laka bidhanbi;
faghfirli fa'innahu la yaghfiru-dh-dhunuba ill a ant a. A'uidhu bika min sharri ma sana'tu.' (O Allah, You are my Lord, there is none worthy of worship except You. You have created me and I am Your slave, and I am adhering to Your covenant and Your promise as much as I can. I seek refuge with You from the evil of what I do. I acknowledge Your blessing and I acknowledge my sin, so forgive me, for there is none who can forgive sin except You) If somebody recites this invocation during the night, and if he should die then, he will go to Paradise (or he will be from the people of Paradise). And if he recites it in the morning, and if he should die on the same day, he will have the same fate."

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، حَدَّثَنَا حُسَيْنٌ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ بُرَيْدَةَ، عَنْ بُشَيْرِ بْنِ كَعْبٍ، عَنْ شَدَّادِ بْنِ أَوْسٍ، عَنِ النَّبِيِّ ﷺ قَالَ " سَيِّدُ الاِسْتِغْفَارِ اللَّهُمَّ أَنْتَ رَبِّي لاَ إِلَهَ إِلاَّ أَنْتَ، خَلَقْتَنِي وَأَنَا عَبْدُكَ، وَأَنَا عَلَى عَهْدِكَ وَوَعْدِكَ مَا اسْتَطَعْتُ، أَبُوءُ لَكَ بِنِعْمَتِكَ، وَأَبُوءُ لَكَ بِذَنْبِي، فَاغْفِرْ لِي، فَإِنَّهُ لاَ يَغْفِرُ الذُّنُوبَ إِلاَّ أَنْتَ، أَعُوذُ بِكَ مِنْ شَرِّ مَا صَنَعْتُ. إِذَا قَالَ حِينَ يُمْسِي فَمَاتَ دَخَلَ الْجَنَّةَ ـ أَوْ كَانَ مِنْ أَهْلِ الْجَنَّةِ ـ وَإِذَا قَالَ حِينَ يُصْبِحُ فَمَاتَ مِنْ يَوْمِهِ ". مِثْلَهُ.