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. (Using translation from Nasāʾī 1301)
أَنَّ رَسُولَ اللهِ ﷺ دَخَلَ الْمَسْجِدَ إِذَا رَجُلٌ قَدْ صَلَّى وَهُوَ يَتَشَهَّدُ فَقَالَ اللهُمَّ إِنِّي أَسْأَلُكُ يَا اللهُ الْوَاحِدُ الْأَحَدُ الصَّمَدُ الَّذِي لَمْ يَلِدْ وَلَمْ يُولَدْ وَلَمْ يَكُنْ لَهُ كُفُوًا أَحَدٌ أَنْ تَغْفِرَ لِي ذُنُوبِي إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمِ فَقَالَ رَسُولُ اللهِ ﷺ «قَدْ غُفِرَ لَهُ» ثَلَاثًا