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Imam Tirmidzi : 1543

حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ الْخَلَّالُ حَدَّثَنَا عَفَّانُ حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ حَدَّثَنَا ثَابِتٌ عَنْ أَنَسٍ قَالَكَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَا يُغِيرُ إِلَّا عِنْدَ صَلَاةِ الْفَجْرِ فَإِنْ سَمِعَ أَذَانًا أَمْسَكَ وَإِلَّا أَغَارَ فَاسْتَمَعَ ذَاتَ يَوْمٍ فَسَمِعَ رَجُلًا يَقُولُ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ فَقَالَ عَلَى الْفِطْرَةِ فَقَالَ أَشْهَدُ أَنْ لَا إِلَهَ إِلَّا اللَّهُ فَقَالَ خَرَجْتَ مِنْ النَّارِقَالَ الْحَسَنُ وَحَدَّثَنَا أَبُو الْوَلِيدِ حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ بِهَذَا الْإِسْنَادِ مِثْلَهُ قَالَ أَبُو عِيسَى وَهَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ

Narrated to us [Al Hasan bin Ali Al Khallal] said, narrated to us [Affan] said, narrated to us [Hammad bin Salamah] said, narrated to us [Tsabit] from [Anas], he said: 'The Prophet, peace and blessings be upon him, never launched a surprise attack except at dawn. If he heard the call to prayer, he refrained, but if not, he attacked. One day, he listened carefully and heard a man saying: Allahu Akbar, Allahu Akbar." He said: "He is upon the fitrah (natural disposition of faith and monotheism)." The man then said: "I bear witness that there is no god but Allah." He said: "You have escaped the Fire." Al Hasan said: 'Narrated to us [Abul Walid] said, narrated to us [Hammad bin Salamah] with this chain, as in this hadith.' Abu Isa said: 'This hadith is hasan sahih.'"