Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "In the Book of Allah there are two verses such that if a servant commits a sin, then recites them and asks Allah for forgiveness, Allah will surely forgive him: 'And those who, when they commit an indecency or wrong themselves, remember Allah and seek forgiveness for their sins - and who forgives sins except Allah?' [Surah Al Imran: 135], and His saying: 'And whoever does evil or wrongs himself, then seeks forgiveness from Allah, will find Allah Forgiving, Merciful' [Surah al-Nisa: 110]."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9003