" Verily! We have sent it (this Qur'aan) down in the Night of Decree (Lailatul-Qadr). And what will make you know what the Night of Decree is? The Night of Decree is better than a thousand months. Therein descend the angels and the Rooh (i.e. Gabriel) by Allaah's Permission with all Decrees, Peace! until the appearance of dawn."
(Al-Qadr 97: 1-5)
إنَّا أَنْزَلْنَاهُ فِي لَيْلَةٍ مُبَارَكَةٍ إِنَّا كُنَّا مُنْذِرِينَ فِيهَا يُفْرَقُ كُلُّ أَمْرٍ حَكِيمٍ أَمْرًا مِنْ عِنْدِنَا إِنَّا
" We sent it (this Qur'aan) down on a blessed Night. Verily, We are ever warning (mankind of Our Torment). Therein (that Night) is decreed every matter of ordainment. Amran (i.e. a command or this Qur'aan or His Decree of every matter) from Us. Verily, We are ever sending (the Messenger). (As) a Mercy from your Lord. Verily! He is the All-Hearer, the All-Knower." (Ad-Dukhaan 44: 3-6)
Lailatul qadr is night power, execellence, miracle. This is the night that the Holy Quran was sent down. This is the night when the malaikah (angels) come down to the earth with grace, blessings and peace. Lailatul qadr is the night free from evil and destruction. The miracle night is filled with the safety of azab (punishment).
One who misses this blessed night then he has missed much good for no one misses it except one from whom it is withheld. Therefore it is recommended that the Muslim who is eager to be obedient to Allah should stand in Prayer during this night out of Iman (faith) and hoping for the great reward, since if he does this, Allah will forgive his previous sins.
Rasulullah said in hadits: "Whoever stands in (Prayer) in Lailatul-Qadr out of Iman (faithful) and seeking reward then his previous sins are forgiven." (Bukhari)