“Verily, We have sent it (this Qur’an) down in the Night of Al-Qadr (Decree). And what will make you know what the Night of Al-Qadr (Decree) is? The Night of Al-Qadr (Decree) is better than a thousand months (i.e., worshipping Allah in that night is better than worshipping Him a thousand months, i.e., 83 years and 4 months). Therein descend the angels and the Ruh [Jibril (Gabriel)] by Allah’s Permission with all Decrees. (All that night), there is peace (and goodness from Allah to His believing slaves) until the appearance of dawn.” (97:1-5)
“We sent it (this Qur’an) down on a blessed night [(i.e., the Night of Al-Qadr, Surah No:97) in the month of Ramadan, the 9th month of the Islamic calendar]. Verily, We are ever warning [mankind that Our Torment will reach those who disbelieve in Our Oneness of Lordship and in Our Oneness of worship]. Therein (that night) is decreed every matter of ordainments (i.e., the matters of deaths, births, provisions, and calamities for the whole (coming) year as decreed by Allah). As a Command (or this Qur’an or the Decree of every matter) from Us. Verily, We are ever sending (the Messengers). (As) a Mercy from your Rubb, Verily! He is the All-Hearer, the All-Knower.” (44:3-6)
Abu Hurairah (May Allah be pleased with him) reported: The Prophet (sallallaahu ’alayhi wa sallam) said, “Whosoever performs Qiyam during Lailat-ul-Qadr (Night of Decree), with Faith and being hopeful of Allah’s reward, will have his former sins forgiven.” [Al-Bukhari and Muslim].
Commentary: Qiyam here means what keeps one awake to one’s capacity and for worship and makes one perform Nawafil, impels one to beg pardon for sins from Allah, urges one to praise Him. Especially, if a person performs ‘Isha prayer and Fajr prayer in congregation, he will hopefully attain all those distinctions which are mentioned in this Hadith.
(Riyad Us-Saliheen, Book of Virtues, Chapter 214, No. 1189)