Laylatul Qadr (the Night of Decree).
“Verily! We have sent it (Quran) 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)
The night of Decree occurs in odd-numbered nights during the last ten days of Ramadan. It may be on twenty-first, twenty-third, twenty-fifth, twenty-seventh or twenty-ninth. It is narrated by Aisha (R.A):
“Allah’s Messenger (P.B.U.H) used to practice Itikaaf in the last ten nights and say: ‘Seek out Lailatul-Qadr in the (odd nights) of the last ten days of Ramadhan.” (Bukhari, Muslim).
In this video, Sheikh Mufti Ismail Menk talks about what we should on the Night of Decree… Watch.