Shaddad bin Aws narrated that:
The Prophet (Muhammad saws ) said to him: “Should I not direct you to the chief of supplications for forgiveness?
‘O Allah, You are my Lord, there is none worthy of worship except You, You created me and I am Your slave. I am adhering to Your covenant and Your promise as much as I am able to, I seek refuge in You from the evil of what I have done. I admit to You your blessings upon me, and I admit to my sins. So forgive me, for there is none who can forgive sins except You
(Allāhumma anta rabbī lā ilāha illā anta, khalaqtanī wa ana `abduka, wa ana `alā `ahdika wa wa`dika ma-staṭa`tu. A`ūdhu bika min sharri ma ṣana`tu, wa abū’u ilayka bini`matika `alayya wa a`tarifu bidhunūbī faghfirlī dhunūbī innahu lā yaghfirudh-dhunūba illā ant).
اللَّهُمَّأَنْتَ رَبِّي لاَ إِلَهَ إِلاَّ أَنْتَ خَلَقْتَنِي وَأَنَا عَبْدُكَ وَأَنَا عَلَى عَهْدِكَ وَوَعْدِكَ مَا اسْتَطَعْتُ أَعُوذُ بِكَ مِنْ شَرِّ مَا صَنَعْتُ وَأَبُوءُ إِلَيْكَ بِنِعْمَتِكَ عَلَىَّ وَأَعْتَرِفُ بِذُنُوبِي فَاغْفِرْ لِي ذُنُوبِي إِنَّهُ لاَ يَغْفِرُ الذُّنُوبَ إِلاَّ أَنْتَ
’ None of you says it when he reaches the evening, and a decree comes upon him before he reaches morning, except that Paradise becomes obligatory upon him. And none says it when he reaches the morning, and a decree comes upon him before he reaches evening, except that Paradise becomes obligatory for him.”
Grade: Sahih (Darussalam)
Jami` at-Tirmidhi Book 48, Hadith 24