When one of you finishes the last tashahhud, he should seek refuge in Allah from four things: the punishment in Hell, the punishment in the grave, the trail of life and death, and the evil of Antichrist.  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا فَرَغَ أَحَدُكُمْ مِنَ التَّشَهُّدِ الآخِرِ فَلْيَتَعَوَّذْ بِاللَّهِ مِنْ أَرْبَعٍ مِنْ عَذَابِ جَهَنَّمَ وَمِنْ عَذَابِ الْقَبْرِ وَمِنْ فِتْنَةِ الْمَحْيَا وَالْمَمَاتِ وَمِنْ شَرِّ الْمَسِيحِ الدَّجَّالِ  

The Prophet ﷺ used to say after the tashahhud: "O Allah, I seek refuge in Thee from the punishment in Hell, and I seek refuge in Thee from the punishment in the grave, and I seek refuge in Thee from the trial of antichrist, and I seek refuge in Thee from the trial of life and death."  

عَنِ النَّبِيِّ ﷺ أَنَّهُ كَانَ يَقُولُ بَعْدَ التَّشَهُّدِ اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنْ عَذَابِ جَهَنَّمَ وَأَعُوذُ بِكَ مِنْ عَذَابِ الْقَبْرِ وَأَعُوذُ بِكَ مِنْ فِتْنَةِ الدَّجَّالِ وَأَعُوذُ بِكَ مِنْ فِتْنَةِ الْمَحْيَا وَالْمَمَاتِ  

The Messenger of Allah ﷺ entered the mosque and saw a man who had finished his prayer, and was reciting the tashahhud saying: O Allah, I ask you, O Allah, the One, the eternally besought of all, He begetteth not, nor was He begotten, and there is none comparable unto Him, that you may forgive me my sins, you are Most Forgiving, Merciful. He (the Prophet) said: He was forgiven (repeating three times.)  

قَالَ دَخَلَ رَسُولُ اللَّهِ ﷺ الْمَسْجِدَ فَإِذَا هُوَ بِرَجُلٍ قَدْ قَضَى صَلاَتَهُ وَهُوَ يَتَشَهَّدُ وَهُوَ يَقُولُ اللَّهُمَّ إِنِّي أَسْأَلُكَ يَا اللَّهُ الأَحَدُ الصَّمَدُ الَّذِي لَمْ يَلِدْ وَلَمْ يُولَدْ وَلَمْ يَكُنْ لَهُ كُفُوًا أَحَدٌ أَنْ تَغْفِرَ لِي ذُنُوبِي إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمُ قَالَ فَقَالَ قَدْ غُفِرَ لَهُ قَدْ غُفِرَ لَهُ ثَلاَثًا