: Verily! We have sent it (this Qur’an) down in the night of al-Qadr.
: And what will make you know what the night of al-Qadr is?
: The night of al-Qadr 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 Jibril by Allah’s permission with all decrees.
: Peace! until the appearance of dawn.
[Surah al-Qadr (97): 1-5]
Imam al-S’adi [d. 1376 AH], may Allah have mercy on him, commented on this Surah by saying:
Allah, the Most High, says: ‘Verily! We have sent it (i.e. this Qur’an) down in the night of al-Qadr.’ – He, the Most High, revealed this verse in order to make clear it’s (i.e the night al-Qadr’s) virtue and its high standing. He, The Most High, also says [in another place in the Qur'an]: ‘Verily! We have sent it (this Qur’an) down on a blessed night.’
What is meant is that Allah, the Most High, sent it down in Ramadan, on the night of al-Qadr. [And by doing so], He, the Most High, showed great mercy to His slaves; and [His] slaves are unable to show [sufficient] thanks for this blessing.
The night of al-Qadr has been named so due to its greatness and virtue to Allah. It has also been named that because it is the night wherein it is decreed what will happen this year. Life spans, provisions and destinies will all be decreed on this night.
[After this verse], Allah, the Most High, magnifies the affair and status of the night of al-Qadr by saying: ‘And what will make you know what the night of al-Qadr is?’ In other words: Indeed its affair is lofty, and its significance is great.
[Then, Allah, the Most High, says]: ‘The night of Al-Qadr 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). – [Noble Qur'an]
Meaning, its virtue is that of a thousand months. Therefore, [a worshipper’s righteous] actions that night are better than worshipping Allah a thousand months, i.e. 83 years and 4 months) other than it.
This is something that bewilders the minds and astonishes the intellects. Allah, the Most High, has bestowed upon this weak nation great strength by providing them with a night wherein their [righteous] actions are equal to and greater than those performed in a thousand months other than it.
[Realize O Muslim], that a life span of eighty years is viewed as a long life; [yet, one is able to achieve a life time of worship in one night].
[Then, Allah, the Most High, says]: Therein descend the angels and the Ruh [Jibril] by Allah’s Permission with all decrees. In other words: The descent of the angels that night is plentiful.
[And in the last verse] He, the Most High, says: ‘Peace! until the appearance of dawn.’ In other words: There is safety that night from all evil and harm, beginning from when the sun sets until the sun has fully risen.
And there are an abundance of Hadeeth discussing its (the night of al-Qadr’s) virtue and that it is in the last ten nights of Ramadan, specifically the odd nights. These characteristics will remain until the [final] hour is established.
For this reason, the Messenger of Allah, used to seclude himself in the Masjid and increase in worship during the last ten nights in Ramadan, hoping that his acts of worship would fall on the night of al-Qadr.
['Abdur-Rahman al-Sa'di, Taysir al-Karim al-Rahman, 790|Source:(embodyislam.org)|Translated by: Abu Adam Jamil Finch|Courtesy of: Qawareer]
In the name of Allah, the Merciful, the Compassionate
(97:1) Behold, We revealed this (Qur’an) on the Night of Power. 
(97:2) And what do you know what the Night of Power is?
(97:3) The Night of Power is better than a thousand months. 
(97:4) The angels along with the Spirit  descend in it by the permission of their Lord  with all kinds of decrees.
(97:5) All peace is that night until the rise of dawn. 
 The words in the original are anzalana hu: We sent it down. But although there is no mention of the Qur’an before it, the Qur’an is implied, for sending down by itself points out that the Qur’an is meant. And there are numerous instances of this in the Qur’an that if from the context, or the style, the antecedent of a pronoun is apparent, the pronoun is used even if the antecedent has not been mentioned anywhere before or after it. (For explanation, see (E.N. 9 of Surah An-Najm).
Here, it has been said: We sent it down (the Qur’an) in the Night of Destiny, and in (Surah Al-Baqarah, Ayat 185), Ramadan is the month in which the Qur’an was sent down. This shows that the night in which the Angel of Allah had brought down revelation for the first time to the Prophet (peace be upon him) in the Cave of Hira, was a night of the month of Ramadan. This night has been described as Laylatul-Qadr here and as Laylat-im-mubarakah in (Surah Ad-Dukhan,Ayat 3).
There can be two meanings of sending down the Qur’an in this night: First, that in this night the entire Qur’an was entrusted to the bearers (angels) of revelation, and then Jibril continued to reveal its verses and Surahs, from time to time, to the Prophet (peace be upon him) during 23 years as the occasion and conditions demanded. This meaning has been given by Ibn Abbas. (Ibn Jarir, Ibn al- Mundhir, Ibn Abi Hatim, Hakim, lbn Marduyah, Baihaqi). Second, that the revelation of the Qur’an began in this night. This is Imam Shafi’s view, although from him too the other view is also related, which is the view of Ibn Abbas as cited above (Ibn Jarir). Anyhow, in both cases, the meaning is the same that the revelation of the Qur’an to the Prophet (peace be upon him) began in this very night, and this was the night in which the five opening verses of (Surah Al-Alaq) were revealed. The fact, however, is that Allah did not compose the verses and the Surahs of the Qur’an right at the time guidance was needed by the Prophet (peace be upon him) for his message of Islam in respect of an occasion or affair, but even before the creation of the universe, in the very beginning, Allah had a full plan of the creation of mankind on the earth, of raising the Prophets in it, of sending down the Books to the Prophets, of raising the Prophet Muhammad (peace be upon him) at the end of the line of the Prophets and of sending down the Qur’an to him. In the Night of Destiny only the execution of the final phase of the plan began. No wonder if at that very time the entire Qur’an was entrusted to the bearers of revelation.
Some commentators have interpreted qadr to mean destiny (taqdir), i.e. it is the night in which Allah entrusts the decrees of destiny to the angels to be enforced. This is supported by (verse 3 of Surah Ad-Dukhan): This is a night in which every matter is decided wisely by Our command. On the contrary, Imam Zuhri says that qadr means glory and honor, there by implying that it is a Night of Destiny. This meaning is supported by the words Laylatul-Qadr is better than a thousand months of this Surah itself.
As for the question as to which night it was, it is disputed and there are as many as 40 different views on this subject. However, a great majority of scholars hold the opinion that one of the odd nights of the last ten nights of the month of Ramadan is Laylatul-Qadr, and among these also most scholars think that it is the 27th night. Below we give the authentic Ahadeeth which have been reported in this connection:
According to Abu Hurairah, the Prophet (peace be upon him) said, in connection with Laylatul-Qadr, that it is the 27th night. (Abu Daud Tayalisi). According to another tradition from Abu Hurairah, it is the last night of Ramadan. (Musnad Ahmad).
When Zirr bin Hubaish asked Ubayy bin Kaab about Laylatul-Qadr, he stated on oath, and did not make any exception, that it is the 27th night. (Ahmad, Muslim, Abu Da’ud, Tirmidhi, Nasai, Ibn Hibban). When Abu Zarr was asked about it, he said: Umar, Hudhaifah and many other companions of the Prophet (peace be upon him) had no doubt that it is the 27th night. (Ibn Abi Shaibah). Ubadah bin as-Samit says that the Prophet (peace be upon him) said: Laylatul-Qadr is one of the odd nights of the last ten nights of Ramadan: 21st, 23rd, 25th, 27th, 29th, or the last night. (Musnad Ahmad).
Abdullah bin Abbas says that the Prophet (peace be upon him) said: Search for it among the last ten nights of Ramadan when there are still nine days in the month, or seven days, or five days. (Bukhari). Most of the scholars have understood it to mean that by this the Prophet (peace be upon him) meant the odd nights. Abu Bakr said: When nine days remain in the month, or seven days, or five days, or three days, or the last night. What he meant was that Laylatul-Qadr should be sought among these days. (Tirmidhi, Nasai).
According to ‘Aaishah, the Prophet (peace be upon him) said: Search for Laylatul-Qadr among the odd nights of the last ten nights of Ramadan. (Bukhari, Muslim, Ahmad, Tirmidhi). ‘Aaishah and Abdullah bin Umar have also reported that the Prophet (peace be upon him) observed i’tikaaf (seclusion in the Mosque) during the last ten nights of Ramadan every year during his lifetime.
On the basis of the traditions related in this regard on the authority of a great companions like Muawiyah, lbn Umar, Ibn Abbas and others, a large number of the earlier scholars regard the 27th of Ramadan as Laylatul-Qadr. Probably Allah and His Messenger have not specified any one night for the reason so that the people, in their zeal to benefit from the virtues of Laylatul-Qadr, should spend more and more nights in worship and devotion and should not remain content with only one night. Here the question arises that when it is night at Makkah, it is daytime in a large part of the world; therefore, the people of those parts can never take advantage of Laylatul-Qadr. The answer is that the word night in Arabic is mostly used for the combination of the day and night. Therefore, the night preceding the day on any one of these dates of Ramadan can be Laylatul-Qadr for that part of the world.
 The commentators in general have understood this to mean that the good acts performed in this night are superior in value to the good acts of a thousand months in which Laylatul-Qadr is not included. There is no doubt that this is in itself correct and the Prophet (peace be upon him) has described great excellences and virtues of the good acts and devotions of this night. According to a tradition related in Bukhari and Muslim, on the authority of Abu Hurairah, the Prophet (peace be upon him) said: The one who remained standing in worship in the state of belief and for the sake of rewards from Allah during Laylatul-Qadr, would have all his previous sins forgiven. And in Musnad Ahmad, there is a tradition from Ubadah bin as-Samit, saying that the Prophet said: Laylatut-Qadr is among the last ten nights of Ramadan. The one who stood up in worship in order to take advantage of their rewards, Allah will forgive all his former and latter sins. But, the verse does not say: To act righteously in Laylatul-Qadr is better than acting righteously in a thousand months, but it says: Laylatul-Qadr is better than a thousand months. And a thousand months also does not imply 83 years and 4 months exactly, but a very long period of time as a thousand denoted among the Arabs. Therefore, the verse means that in this one night a task was accomplished for the welfare of mankind the like of which had not been accomplished even during an indefinitely long period of history.
 The Spirit: Jibril (Gabriel), who has been mentioned separately from the angels in view of his unique eminence, honor and merit.
 That is, they do not descend of their own accord but by leave of their Lord, and every decree implies amr hakim (a wise decree) as described in (Surah Ad-Dukhan, Ayat 5).
 That is, the entire night, from evening till morning, is peace, free from every evil and mischief.