The Master Supplication for Forgiveness (Sayyid al-Istighfar)
اللَّهُمَّ أَنْتَ رَبِّي لَا إِلَهَ إِلَّا أَنْتَ، خَلَقْتَنِي وَأَنَا عَبْدُكَ، وَأَنَا عَلَى عَهْدِكَ وَوَعْدِكَ مَا اسْتَطَعْتُ، أَعُوذُ بِكَ مِنْ شَرِّ مَا صَنَعْتُ، أَبُوءُ لَكَ بِنِعْمَتِكَ عَلَيَّ، وَأَبُوءُ بِذَنْبِي فَاغْفِرْ لِي فَإِنَّهُ لَا يَغْفِرُ الذُّنُوبَ إِلَّا أَنْتَ.
How it is read
Allahumma Anta Rabbee la ilaha illa Ant, khalaqtanee wa ana 'abduk, wa ana 'ala 'ahdika wa wa'dika mas-tata't. A'udhu bika min sharri ma sana't, aboo-u laka bi-ni'matika 'alay, wa aboo-u bi-dhambee faghfir lee fa-innahu la yaghfirudh-dhunooba illa Ant.
What it means
O Allah, You are my Lord, there is no deity worthy of worship except You. You created me and I am Your slave, and I abide by Your covenant and promise as best I can. I seek refuge in You from the evil of what I have done. I acknowledge Your favor upon me, and I acknowledge my sin, so forgive me, for none forgives sins except You.
Where it comes from
Sahih al-Bukhari (6306)