وَعَنْ أَبِي بَكْرٍ اَلصِّدِّيقِ رضى الله عنه
«أَنَّهُ قَالَ لِرَسُولِ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَلِّمْنِي دُعَاءً أَدْعُو بِهِ فِي صَلَاتِي. قَالَ قُلْ: «اَللَّهُمَّ إِنِّي ظَلَمْتُ نَفْسِي ظُلْمًا كَثِيرًا، وَلَا يَغْفِرُ اَلذُّنُوبَ إِلَّا أَنْتَ، فَاغْفِرْ لِي مَغْفِرَةً مِنْ عِنْدِكَ، وَارْحَمْنِي، إِنَّكَ أَنْتَ اَلْغَفُورُ اَلرَّحِيمُ» مُتَّفَقٌ عَلَيْهِ. 11 صحيح
He said to the Messenger of Allah (sallallahu alayhi wa sallam), “Teach me a supplication to use in my prayer.” He (sallallahu alayhi wa sallam) said: “Say: O Allah, I have greatly wronged myself, and no one forgives sins except You, so grant me forgiveness from You and have mercy on me, You are the Forgiving and the Merciful One.”.
Bulugh al-Maram 387, Book 2, The Book of Prayer, Hadith 208. 1 min read