Laylat al-Qadr commemorates the night in 610 CE during which Allah revealed the entire Qur’an to Muhammad. It was then that the angel Gabriel first spoke to him, and was thus the beginning of his mission. These revelations continued throughout the remainder of his life. The common belief that this day occurred on the 26th or 27th of Ramadan has no Islamic base. It seems to have originated in Manicheism, where the death of Mani is celebrated on the 27th of the fasting month. This day is also known as the Night of Power or Night of Destiny. Discuss
Source: The Free Dictionary