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كتاب العلم
3  
Knowledge
(30)
Chapter: Repeating ones talk thrice in order to make others understand
(30)
باب مَنْ أَعَادَ الْحَدِيثَ ثَلاَثًا لِيُفْهَمَ عَنْهُ
Sahih al-Bukhari 96

Narrated `Abdullah bin `Amr:

Once Allah's Messenger (ﷺ) remained behind us in a journey. He joined us while we were performing ablution for the `Asr prayer which was over-due. We were just passing wet hands over our feet (not washing them properly) so the Prophet (ﷺ) addressed us in a loud voice and said twice or thrice, "Save your heels from the fire."

حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ أَبِي بِشْرٍ، عَنْ يُوسُفَ بْنِ مَاهَكَ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ تَخَلَّفَ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي سَفَرٍ سَافَرْنَاهُ فَأَدْرَكَنَا وَقَدْ أَرْهَقْنَا الصَّلاَةَ صَلاَةَ الْعَصْرِ وَنَحْنُ نَتَوَضَّأُ، فَجَعَلْنَا نَمْسَحُ عَلَى أَرْجُلِنَا، فَنَادَى بِأَعْلَى صَوْتِهِ ‏ "‏ وَيْلٌ لِلأَعْقَابِ مِنَ النَّارِ ‏"‏‏.‏ مَرَّتَيْنِ أَوْ ثَلاَثًا‏.‏
Reference : Sahih al-Bukhari 96
In-book reference : Book 3, Hadith 38
USC-MSA web (English) reference : Vol. 1, Book 3, Hadith 96
  (deprecated numbering scheme)