NASAI-KUBRA 1271:
from Muslim b. Abū Bakrah —
"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)
الكبرى للنسائي ١٢٧١:
عن مسلم بن ابو بكره —
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
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