Narrated `Amr bin Maimun Al-Audi: Sa`d used to teach his sons the following words as a teacher teaches his students the skill of writing and used to say that Allah's Messenger (ﷺ) used to seek Refuge with Allah from them (i.e. the evils) at the end of every prayer. The words are: 'O Allah! I seek refuge with You from cowardice, and seek refuge with You from being brought back to a bad stage of old life and seek refuge with You from the afflictions of the world, and seek refuge with You from the punishments in the grave.'
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا أَبُو عَوَانَةَ، حَدَّثَنَا عَبْدُ الْمَلِكِ بْنُ عُمَيْرٍ، سَمِعْتُ عَمْرَو بْنَ مَيْمُونٍ الأَوْدِيَّ، قَالَ كَانَ سَعْدٌ يُعَلِّمُ بَنِيهِ هَؤُلاَءِ الْكَلِمَاتِ كَمَا يُعَلِّمُ الْمُعَلِّمُ الْغِلْمَانَ الْكِتَابَةَ، وَيَقُولُ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَتَعَوَّذُ مِنْهُنَّ دُبُرَ الصَّلاَةِ " اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الْجُبْنِ، وَأَعُوذُ بِكَ أَنْ أُرَدَّ إِلَى أَرْذَلِ الْعُمُرِ، وَأَعُوذُ بِكَ مِنْ فِتْنَةِ الدُّنْيَا، وَأَعُوذُ بِكَ مِنْ عَذَابِ الْقَبْرِ ". فَحَدَّثْتُ بِهِ مُصْعَبًا فَصَدَّقَهُ.
sunnah.com