Qur'an, Al-Qadr, Surah 97:1-5
Behold, We revealed the Qur'an on the Night of Power. If only you knew what the Night of Power is. That one night surpasses a thousand months, for the angels and the Spirit [Gabriel] descend to the earth, bearing divine inspiration by the permission of their Lord. That night is the night of peace until the crack of dawn.