Musnad Ahmad 658:165

Hujayn narrated to us, Israel narrated to us, from Abu Ishaq, from Al-Bara’ who said: While a man from the companions of the Prophet, may God bless him and grant him peace, was praying, and he had a horse tied in the house, it began to shy away. The man went out and looked, but he did not see anything, and it continued to shy away. When morning came, he mentioned that to the Prophet, may God bless him and grant him peace, and he said: "That was the tranquility (al-sakinah) that descended with the Quran."