Sayyiduna Abdullah bin Amr bin al-As narrates that Abu Bakr Siddiq (may Allah be pleased with him) said to the Messenger of Allah (peace and blessings be upon him): "O Messenger of Allah (peace and blessings be upon him), teach me a supplication which I may recite in my prayer and in my home." The Prophet (peace and blessings be upon him) said: "Recite this supplication «‏‏‏‏اللّٰهُمَّ إِنِّي ظَلَمْتُ نَفْسِي ظُلْمًا كَبِيرًا وَلَا يَغْفِرُ الذُّنُوبَ إِلَّا أَنْتَ، فَاغْفِرْ لِي مَغْفِرَةً مِنْ عِنْدِكَ، وَارْحَمْنِي إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمُ» ‏‏‏‏ 'O Allah, indeed I have wronged myself greatly, and there is none who forgives sins except You, so grant me forgiveness and mercy from Yourself, surely You are the Most Forgiving, Most Merciful.'"