"My father used to say following every prayer: 'Allahumma inni a-udhu bika min al-kufri wal-faqri wa 'adhab al-qabr. ( O Allah, I seek refuge with You from Kufr, poverty, and the torment of the grave)' and I used to say them (these words). My father said: 'O my son, from whom did you learn this?' I said: 'From you. He said: "The Messenger of Allah ﷺ used to say them following the prayer.'" (Using translation from Nasāʾī 1347)  

كَانَ أَبِي يَقُولُ فِي دُبُرِ الصَّلَاةِ «اللهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الْكُفْرِ وَالْفَقْرِ وَعَذَابِ الْقَبْرِ» فَكُنْتُ أَقُولُهُنَّ فَقَالَ أَبِي عَمَّنْ أَخَذْتَ هَذَا؟ قُلْتُ عَنْكَ قَالَ إِنَّ رَسُولَ اللهِ ﷺ كَانَ يَقُولُهُنَّ فِي دُبُرِ الصَّلَاةِ  

He heard his father say following the prayer: "Allahumma inni a'udhu bika minal-kufri wal-faqri, wa 'adhabil-qabri (O Allah, I seek refuge with You from Kufr, poverty and the torment of the grave.)" I started to recite them and he said: "O my son, where did you learn these words?" I said: "O my father, I heard you saying this supplication at the end of the prayer, and I learned them from you." He said: "Continue to recite them, O my son, for the Prophet of Allah [SAW] used to say this supplication at the end of the prayer." (Using translation from Nasāʾī 5465)  

سَمِعَ وَالِدَهُ يَقُولُ فِي دُبُرِ الصَّلَاةِ «اللهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الْكُفْرِ وَالْفَقْرِ وَعَذَابِ الْقَبْرِ» فَجَعَلْتُ أَدْعُو بِهِنَّ فَقَالَ يَا بُنَيَّ أَنَّى عَلِمْتَ هَؤُلَاءِ الْكَلِمَاتِ؟ قَالَ يَا أَبَهْ سَمِعْتُكَ تَدْعُو بِهِنَّ فِي دُبُرِ الصَّلَاةِ فَأَخَذْتُهُنَّ عَنْكَ قَالَ فَالْزَمْهُنَّ يَا بُنَيَّ فَإِنَّ نَبِيَّ اللهِ ﷺ كَانَ يَدْعُو بِهِنَّ فِي دُبُرِ الصَّلَاةِ