While a man from the companions of the Prophet ﷺ was reciting (Qur'an) and his horse was tied in the house, the horse got startled and started jumping. The man came out, looked around but could not find anything, yet the horse went on jumping. The next morning he mentioned that to the Prophet. The Prophet ﷺ said, "That was the tranquility (calmness) which descended because of the recitation of the Qur'an." (Using translation from Bukhārī 4839)  

بَيْنَمَا رَجُلٌ مِنْ أَصْحَابِ النَّبِيِّ ﷺ يُصَلِّي وَفَرَسٌ لَهُ حِصَانٌ مَرْبُوطٌ فِي الدَّارِ فَجَعَلَ يَنْفِرُ فَخَرَجَ الرَّجُلُ فَنَظَرَ فَلَمْ يَرَ شَيْئًا وَجَعَلَ يَنْفِرُ فَلَمَّا أَصْبَحَ ذَكَرَ ذَلِكَ لِلنَّبِيِّ ﷺ فَقَالَ تِلْكَ السَّكِينَةُ نَزَلَتْ بِالْقُرْآنِ