Sahih Muslim , Hadith 795

Al-Bara' reported that a person was reciting Surat al-Kahf and there was a horse tied with two ropes at his side, a cloud overshadowed him, and as it began to come nearer and nearer his horse began to take fright from it. He went and mentioned that to the Prophet in the morning, and he (the Holy Prophet) said: That was tranquillity which came down at the recitation of the Qur'an.

وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا أَبُو خَيْثَمَةَ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْبَرَاءِ، قَالَ كَانَ رَجُلٌ يَقْرَأُ سُورَةَ الْكَهْفِ وَعِنْدَهُ فَرَسٌ مَرْبُوطٌ بِشَطَنَيْنِ فَتَغَشَّتْهُ سَحَابَةٌ فَجَعَلَتْ تَدُورُ وَتَدْنُو وَجَعَلَ فَرَسُهُ يَنْفِرُ مِنْهَا فَلَمَّا أَصْبَحَ أَتَى النَّبِيَّ صلى الله عليه وسلم فَذَكَرَ ذَلِكَ لَهُ فَقَالَ ‏ "‏ تِلْكَ السَّكِينَةُ تَنَزَّلَتْ لِلْقُرْآنِ ‏" ‏ ‏.‏

sunnah.com

Ibn Ishaq reported: I heard al-Bara' as saying that a man recited al-Kahf when an animal was there in the house and it began to take fright. And as he looked around, he found a cloud overshadowing it. He mentioned that to the Messenger of Allah. Upon this he said: O so and so, recite on (the surah) as- Sakina descends at the (recitation of the Qur'an) or on account (of the recitation) of the Qur'an.

وَحَدَّثَنَا ابْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ - وَاللَّفْظُ لاِبْنِ الْمُثَنَّى - قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ، جَعْفَرٍ حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، قَالَ سَمِعْتُ الْبَرَاءَ، يَقُولُ قَرَأَ رَجُلٌ الْكَهْفَ وَفِي الدَّارِ دَابَّةٌ فَجَعَلَتْ تَنْفِرُ فَنَظَرَ فَإِذَا ضَبَابَةٌ أَوْ سَحَابَةٌ قَدْ غَشِيَتْهُ قَالَ فَذَكَرَ ذَلِكَ لِلنَّبِيِّ صلى الله عليه وسلم فَقَالَ ‏ "‏ اقْرَأْ فُلاَنُ فَإِنَّهَا السَّكِينَةُ تَنَزَّلَتْ عِنْدَ الْقُرْآنِ أَوْ تَنَزَّلَتْ لِلْقُرْآنِ ‏" ‏ ‏.‏

sunnah.com

This hadith has been narrated on the authority of al-Bara' with a slight modification of words.

وَحَدَّثَنَا ابْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، وَأَبُو دَاوُدَ قَالاَ حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، قَالَ سَمِعْتُ الْبَرَاءَ، يَقُولُ ‏.‏ فَذَكَرَا نَحْوَهُ غَيْرَ أَنَّهُمَا قَالاَ تَنْقُزُ ‏.‏

sunnah.com