رَبَّنَا ظَلَمْنَا أَنْفُسَنَا وَإِنْ لَمْ تَغْفِرْ لَنَا وَتَرْحَمْنَا لَنَكُونَنَّ مِنَ الْخَاسِرِينَ
Rabbana zalamna anfusana wa in lam taghfir lana wa tarhamna lanakuanna minal-khasirin
Señor nuestro, nos hemos hecho daño a nosotros mismos. Si no nos perdonas y no nos tienes misericordia, seremos ciertamente de los perdedores.
Recite when seeking forgiveness for sins and mistakes
This was the first dua of repentance taught to humanity. Adam and Hawwa (Eve) said this after their sin, and Allah accepted their repentance.