Hanzalah bin 'Ali narrated that:

Mihjan bin Al-Adra' narrated to him that the Messenger of Allah ﷺ entered the masjid and there was a man who had finished his prayer and he was reciting the tashahhud. He said: "Allahumma inni as'aluka ya Allah! Bi-annakal-Wahidul-Ahad us-Samad, alladhi lam yalid wa lam yowled, wa lam yakun lahu kufuwan ahad, an taghfirali dhunubi, innaka antal-Ghafurur-Rahim (O Allah, I ask of You, O Allah, as You are the One, the Only, the Self-Sufficient Master, Who begets not nor was He begotten, and there is None equal or comparable to Him, forgive me my sins, for You are the Oft-Forgiving, Most Merciful.)" The Messenger of Allah ﷺ said: "He has been forgiven," three times.

أَخْبَرَنَا عَمْرُو بْنُ يَزِيدَ أَبُو بُرَيْدٍ الْبَصْرِيُّ، عَنْ عَبْدِ الصَّمَدِ بْنِ عَبْدِ الْوَارِثِ، قَالَ حَدَّثَنَا أَبِي قَالَ، حَدَّثَنَا حُسَيْنٌ الْمُعَلِّمُ، عَنِ ابْنِ بُرَيْدَةَ، قَالَ حَدَّثَنِي حَنْظَلَةُ بْنُ عَلِيٍّ، أَنَّ مِحْجَنَ بْنَ الأَدْرَعِ، حَدَّثَهُ أَنَّ رَسُولَ اللَّهِ ﷺ دَخَلَ الْمَسْجِدَ إِذَا رَجُلٌ قَدْ قَضَى صَلاَتَهُ وَهُوَ يَتَشَهَّدُ فَقَالَ اللَّهُمَّ إِنِّي أَسْأَلُكَ يَا اللَّهُ بِأَنَّكَ الْوَاحِدُ الأَحَدُ الصَّمَدُ الَّذِي لَمْ يَلِدْ وَلَمْ يُولَدْ وَلَمْ يَكُنْ لَهُ كُفُوًا أَحَدٌ أَنْ تَغْفِرَ لِي ذُنُوبِي إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمُ . فَقَالَ رَسُولُ اللَّهِ ﷺ " قَدْ غُفِرَ لَهُ " . ثَلاَثًا .