Volume 6, Book 61, Number 531:
Narrated Al-Bara’:
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 said, “That was As-Sakina (tranquility) which descended be –
cause of (the recitation of) the Qur’an.”