“That was As-Sakina (tranquility)
A man was reciting Surat Al-Kahf and his horse was tied with two ropes beside him.
A cloud came down and spread over that man, and it kept on coming closer and closer to him till his horse started jumping (as if afraid of something).
When it was morning, the man came to the Prophet, and told him of that experience.
The Prophet (ﷺ) said, “That was As-Sakina (tranquility) which descended because of (the recitation of) the Qur’an.”
Sahih al-Bukhari 5011 In-book reference: Book 66, Hadith 33