عَنْ مِحْجَنِ بْنِ الْأَدْرَعِ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ دَخَلَ الْمَسْجِدَ فَإِذَا هُوَ بِرَجُلٍ قَدْ قَضَى صَلَاتَهُ وَهُوَ يَتَشَهَّدُ وَهُوَ يَقُولُ: اللَّهُمَّ إِنِّي أَسْأَلُكَ يَا اللَّهُ الْوَاحِدُ الْأَحَدُ الصَّمَدُ الَّذِي لَمْ يَلِدْ وَلَمْ يُولَدْ وَلَمْ يَكُنْ لَهُ كُفُوًا أَحَدٌ أَنْ تَغْفِرَ لِي ذُنُوبِي إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمُ، قَالَ: فَقَالَ نَبِيُّ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((قَدْ غُفِرَ لَهُ، قَدْ غُفِرَ لَهُ، قَدْ غُفِرَ لَهُ)) ثَلَاثَ مَرَّاتٍ
It is narrated from Sayyiduna Mihjan bin Adra’ (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) entered the mosque and saw a man who, after completing his prayer, was reciting this supplication in the Tashahhud: “O Allah! Indeed, I ask You, O Allah, the One, the Unique, the Self-Sufficient, Who neither begets nor is begotten, and there is none comparable to Him, that You forgive my sins. Indeed, You are the Most Forgiving, Most Merciful.” The Prophet (peace and blessings be upon him) said: “Indeed, he has been forgiven, indeed, he has been forgiven, indeed, he has been forgiven.” That is, he said it three times.