Allah (SWT) says -

إِنَّا أَنزَلْنَاهُ فِي لَيْلَةِ الْقَدْرِ ﴿١﴾ وَمَا أَدْرَاكَ مَا لَيْلَةُ الْقَدْرِ ﴿٢﴾ لَيْلَةُ الْقَدْرِ خَيْرٌ مِّنْ أَلْفِ شَهْرٍ ﴿٣﴾ تَنَزَّلُ الْمَلَائِكَةُ وَالرُّوحُ فِيهَا بِإِذْنِ رَبِّهِم مِّن كُلِّ أَمْرٍ ﴿٤﴾ سَلَامٌ هِيَ حَتَّىٰ مَطْلَعِ الْفَجْرِ ﴿٥﴾

Innaaa anzalnaahu fee Lailatil-Qadr. Wa maaa adraaka maa Lailatul-Qadr. Lailatul-Qadri khairum-min alfi shahr. Tanazzalul-malaaa'ikatu war-Roohu feehaa bi-izni Rabbihim min kulli amr. Salaamun hiya hattaa matla'il-fajr.

(1) Indeed, We sent the Qur'an down during the Night of Decree. (2) And what can make you know what is the Night of Decree? (3) The Night of Decree is better than a thousand months. (4) The angels and the Spirit descend therein by permission of their Lord for every matter. (5) Peace it is until the emergence of dawn.

Reference: Surah Al-Qadr 97:1-5