Du'a for forgiveness: There is no God save Thee

لَّآ إِلَٰهَ إِلَّآ أَنتَ سُبۡحَٰنَكَ إِنِّي كُنتُ مِنَ ٱلظَّٰلِمِينَ

La illaha illa Anta Subhanak, inni kuntu min adh-dhalimeen

There is no God save Thee. Be Thou Glorified! Lo! I have been a wrong-doer

Qur'an 21:87 (Al-Anbiya)