Allah Said;
إِنَّا أَنزَلْنَاهُ فِي لَيْلَةِ الْقَدْرِ
Verily, We have sent it down in the Night of Al-Qadr.
The Virtues of the Night of Al-Qadr (the Decree)
Allah informs that He sent the Qur'an down during the Night of Al-Qadr, and it is a blessed night about which Allah says,
إِنَّأ أَنزَلْنَـهُ فِى لَيْلَةٍ مُّبَـرَكَةٍ
We sent it down on a blessed night. (44;3)
This is the Night of Al-Qadr and it occurs during the month of Ramadan.
This is as Allah says,
شَهْرُ رَمَضَانَ الَّذِى أُنزِلَ فِيهِ الْقُرْانُ
The month of Ramadan in which was revealed the Qur'an. (2;185)
Ibn Abbas and others have said,
"Allah sent the Qur'an down all at one time from the Preserved Tablet (Al-Lawh Al-Mahfuz) to the House of Might (Baytul-`Izzah), which is in the heaven of this world. Then it came down in parts to the Messenger of Allah based upon the incidents that occurred over a period of twenty-three years."
Then Allah magnified the status of the Night of Al-Qadr, which He chose for the revelation of the Mighty Qur'an, by His saying,
وَمَا أَدْرَاكَ مَا لَيْلَةُ الْقَدْرِ