حَدَّثَنَا مَحْمُودُ بْنُ غَيْلاَنَ، حَدَّثَنَا أَبُو دَاوُدَ، أَنْبَأَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، قَالَ سَمِعْتُ الْبَرَاءَ، يَقُولُ بَيْنَمَا رَجُلٌ يَقْرَأُ سُورَةَ الْكَهْفِ إِذْ رَأَى دَابَّتَهُ تَرْكُضُ فَنَظَرَ فَإِذَا مِثْلُ الْغَمَامَةِ أَوِ السَّحَابَةِ فَأَتَى رَسُولَ اللَّهِ صلى الله عليه وسلم فَذَكَرَ ذَلِكَ لَهُ ‏.‏ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ تِلْكَ السَّكِينَةُ نَزَلَتْ مَعَ الْقُرْآنِ أَوْ نَزَلَتْ عَلَى الْقُرْآنِ ‏"‏ ‏.‏ وَفِي الْبَابِ عَنْ أُسَيْدِ بْنِ حُضَيْرٍ ‏.‏ قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ ‏.‏

Narrated Abu Ishaq: hearing Al-Bara say: "There was a man reciting [Surat] Al-Kahf when he saw his riding animal stamping his feet, so he looked and there was something like a shadow or cloud, so he went to the Messenger of Allah (PBUH) and mentioned that to him. The Prophet (PBUH) said: "That was the tranquility which descends with the Qur'an, or descends because of the Qur'an." Translation Not Available

Book reference: Jamiya Tirmidhi Book 45 Hadith 2885
Web reference: Jamiya Tirmidhi Volume 5 Book 42 Hadith 2885