Messenger of Allah (Sallallaahu Alayhi Wasallam) said:
"Whosoever performs the night prayer on the night of Al-Qadr with emaan (firm belief) and seeking reward will have all his past sins forgiven." [Al-Bukhari 4/2550]
This hadeeth is evidence for the virtue of the night of Al-Qadr as well as performing qiyaam during it. And it indicates that it is a grand night, which Allah has honoured and made better than a thousand months in regards to its blessing and the blessings found in the righteous deeds that are performed in it. Thus it is better than the worship of a thousand months and that is equivalent to eighty three years and four months. Due to this, whoever performs qiyaam (night prayer) with true faith and while seeking reward in it, will be forgiven his past sins. There were certain verses verses concerning this virtue:
"We sent it down during a Blessed Night: for We (ever) wish to warn (against Evil). In that (Night) is made distinct every affair of wisdom," [Surah Al Dukhan 44:3-4]
Therefore, it is a 'blessed night' meaning it possesses much good and blessing due to its merit and the great reward that awaits the one who does good deeds in it. Among its blessings, is that Allah revealed the Quran in it. Allah says:
"We have indeed revealed this (Message) in the Night of Power: And what will explain to thee what the night of power is? The Night of Power is better than a thousand months. Therein come down the angels and the Spirit by Allah's permission, on every errand: Peace!...This until the rise of morn!" [Surah Al Qadr 97:1-5]
Ibn Kathir said concerning Allah’s saying:
“‘Therein come down the angels and the Spirit’. This means that the descending of the angels increases during this night due to the vast amount of its blessings. And the angels descend along with the descent of blessing and mercy, just as they descend during the time when the Quran is recited and encompass the gatherings in which Allah is remembered and spread their wings for the true seeker of knowledge, showing respect for him.”
This night occurs only in Ramadan, since Allah revealed the Quran in it. He informs us that its revelation occurred during the month of Ramadan in His saying:
"We have indeed revealed this (Message) in the Night of Power:" And His saying: "Ramadan is the (month) in which was sent down the Quran..." [Surah Al Baqarah 2:185] This means that its revelation from Allah to His Prophet Muhammad (Sallallaahu Alayhi Wasallam) began in it. Allah’s statement: 'the Night of Power (Al-Qadr)' is either an indicative of the honor and station of that night, as it is said: "Such and such person has great Qadr". The conjunction of "the night" to Al-Qadr is the joining of a descriptive feature to it, thus making it mean; "An honorable night". The word 'Al-Qadr' may also be in reference to the ordainment and disposal of affairs. Thus, its being joined to the word "the night" would be in order to denote a place or time to it. So it would mean "the night in which all that will occur in the following year will be decreed." This is similar to Allah's saying: "In that (Night) is made distinct every affair of wisdom,"
Qataadah said: "Therein is decreed every matter of the (upcoming) year"[Reported by At-Tabaree in his Tafseer (25/65) as well as Al -Baihaqee in his book Fadaa'il-ul-Awqaat (pg 216). Its chain of narration is saheeh.] and Ibn Al-Qayyim said that “this is the correct opinion.”[Shifaa' -ul-'Aleel of Ibn Qayyim (pg. 42)]
What seems most correct is that there is nothing that restricts the possibility of these two understandings and Allah knows best.
Prophet Muhammad (Sallallaahu Alayhi Wasallam) statement: 'with emaan' means with firm conviction in what Allah has prepared for those who stand in prayer during this magnificent night. And 'seeking reward' means looking for reward and the attainment of recompense. Thus, this is a grand night, which Allah has chosen for beginning the revelation of the Quran. So the Muslim must acknowledge its weight in worth, by guarding it and spending it in worship whilst having firm conviction and seeking the reward of Allah, in order that Allah may forgive all of his previous sins. This is why the Prophet (Sallallaahu Alayhi Wasallam) warned us about being heedless of this night and being neglectful of spending it in worship, for the Muslim would be prevented from its good.
Abu Hurairah reported that the Messenger of Allah (sallAllahu alayhi wasallam) said: "Ramadan has come to you - a blessed month. Allah has made it obligatory upon you to fast in it. During this month, the gates of heaven are open, the gates of the Hellfire are closed and the evil devils are chained. To Allah belongs a night in it, which is better than a thousand months. Whosoever is prevented from its good, then he has been prevented." [reported Ahmad and An-Nasaa'ee]
The Muslim should supplicate much on the nights in which the night of Al-Qadr is sought. And he should supplicate with that which the Prophet (sallAllahu alayhi wasallam) instructed ‘A’ishah with, when she asked him: 'What if I know on which night the night of Al-Qadr occurs, what should I say?' So he (sallAllahu alayhi wasallam) said: 'Say:O Allah, indeed you are All-Pardoning. You love forgiveness, so forgive me.'
Ibn Kathir said: "It is recommended to supplicate a lot at all times and (to supplicate) more than that during the month of Ramadan, its last ten days and its odd days. And it is highly recommended to increase ones invoking with this supplication: ‘O Allah, indeed you are All-Pardoning. You love forgiveness, so forgive me.’"