Laylat al-Qadr

It is narrated from Sayyiduna al-Faltan bin Asim (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Indeed the Night of Decree was shown to me, then I was made to forget it. I also saw the Messiah of misguidance (the Dajjal), and I saw two men quarrelling with each other, so I separated them, and I was made unmindful of them (the exact details of both matters). As for the Night of Decree, seek it in the last ten (nights of Ramadan); and as for the Messiah of misguidance, he is a man with a broad forehead whose left eye is effaced (sightless); his chest is broad and redness dominates his complexion (as though blood were showing through his body); in appearance he looks exactly like so-and-so bin Abd al-Uzza or Abd al-Uzza bin so-and-so."

It is narrated from Sayyiduna al-Faltan (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever among you is seeking the Night of Decree, let him seek it in the last ten (nights of the blessed month of Ramadan)."
This hadith has been quoted here in abridged form.

My father related: I narrated this hadith to Sayyiduna Ibn Abbas (may Allah be pleased with them both), and he said: What is there in that to surprise you? It was the practice of Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) that when he called the senior elders among the Companions of the Messenger of Allah (peace and blessings be upon him), he would invite me along with them, and he would say: Remain silent until these people speak. Then one day, or one night, he called us and said: The Messenger of Allah (peace and blessings be upon him) said about the Night of Decree what you already know: "Seek it in the odd nights of the last ten." So which odd night is it? A man, giving his own opinion, said that it is the ninth, the seventh, the fifth or the third night. Then Sayyiduna Umar (may Allah be pleased with him) said to me: O Ibn Abbas, why do you not speak? I said: O Commander of the Believers, if you wish, I will speak. He said: I called you only so that you would speak. I said that I would present my own opinion. He said: It is your opinion that I want to know. I said: I have seen in the speech of Allah Almighty that He has mentioned the number seven frequently; thus He created seven heavens and seven earths, until in His speech He also said that the earth brought forth seven kinds of things. Sayyiduna Umar (may Allah be pleased with him) said: I have understood the rest of what you said, but what do you mean by saying that the earth brought forth seven things? I said that Allah Almighty says: "Then We split the earth, cleaving it well, and caused grain to grow therein, and grapes and fodder, and olives and date palms, and dense gardens, and fruit and pasture, as provision for you" [Surah Abasa: 26-32]. So 'hada'iq' means every garden whose trees are dense, and 'abb' is the vegetation that the earth brings forth which people do not eat. Hearing this, Sayyiduna Umar (may Allah be pleased with him) said (to the Companions): Are you unable even to say the like of what this youth has said, the hair of whose head has not yet even evened out? Then he said to me: I had forbidden you from speaking in front of these elders, but now, whenever I call you, do speak in front of them.
I (Ibn Hajar) say: Imam Ahmad (may Allah have mercy on him) narrated from it only the marfu' hadith of Sayyiduna Umar (may Allah be pleased with him).

It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that his student Marthad (the father of Malik) asked him: Did you hear the Messenger of Allah (peace and blessings be upon him) mention the Night of Decree? He replied: Yes. I said (in the presence of the Messenger): O Messenger of Allah, tell me about the Night of Decree: is it in Ramadan or outside Ramadan? He (peace and blessings be upon him) said: "Rather, it is in Ramadan." I said: O Messenger of Allah, is this virtue only for as long as the prophets are present, so that when the prophets depart from the world it too will be taken up, or will it remain until the Day of Resurrection? He (peace and blessings be upon him) said: "No, rather it will remain (every year) until the Day of Resurrection." I asked again: O Messenger of Allah, tell me in which part of Ramadan it is. He (peace and blessings be upon him) said: "In the last ten nights of Ramadan; do not ask me about anything (concerning it) after this." I said (again, out of eagerness): O Messenger of Allah, I adjure you by the right I have over you, tell me which of these ten nights it is. At this he (peace and blessings be upon him) became so angry with me that he had never been angry with me like that before, nor was he ever angry like that afterwards, and he said: "Had Allah willed, He would have informed you of it definitively. Seek it in the last seven nights (of Ramadan), and do not ask me anything further about it now."

Marthad (or Ibn Marthad), the student of Sayyiduna Abu Dharr (may Allah be pleased with him), narrates from his father: I was present with Sayyiduna Abu Dharr (may Allah be pleased with him) when he was asked about the Night of Decree, and he mentioned it (like the previous narration) until he reached the words "the last ten," and he did not mention what comes after it.
I (Ibn Hajar) say: This chain is hasan sahih; and Imam Ahmad and Imam al-Nasa'i also narrated it from the hadith of Abu Zumayl, but not in full.
In the narration of Abu Bakr bin Abi Shaybah there is this addition: I said: O Messenger of Allah, tell us about it (this night). He (peace and blessings be upon him) said: "Had I been permitted to inform (you) about it, I would certainly have informed you of it."
Imam Musaddad also narrated, with his chain, from Malik bin Marthad, from his father Marthad, who said: I asked Sayyiduna Abu Dharr (may Allah be pleased with him), and then he narrated a hadith like it.

Abu Hazim, the freed slave of Banu Hudhayl, narrates: I observed i'tikaf in the mosque of Madinah during the last ten nights of Ramadan together with a man of Banu Bayadah from among the Companions of the Prophet (peace and blessings be upon him), in a small tent of his whose doorway was screened with a piece of reed mat. He said: While we were in the mosque, and the Messenger of Allah (peace and blessings be upon him) was in a tent of his own, he lifted the mat from the doorway and gestured to those in the mosque to gather. So we gathered, and the Messenger of Allah (peace and blessings be upon him) gave us an admonition the like of which I have never heard from any admonisher. He said: "When one of you stands to pray, he is speaking intimately with his Lord, the Blessed and Exalted, so let him look to what he speaks to Him with; and let none of you recite the Qur'an aloud over another." Then he let the mat fall back, and each of us returned to his place. Some of us said to others: This night must have a special significance, since the Messenger of Allah (peace and blessings be upon him) admonished us in it. And it turned out to be the night of the twenty-third.
Imam al-Nasa'i (may Allah have mercy on him) narrated it in the Book of I'tikaf through several chains, most of which are narrations of Abu Hazim from Sayyiduna al-Bayadi (may Allah be pleased with him).
Imam Ahmad (may Allah have mercy on him) narrated the incident of the prohibition of reciting aloud (in prayer) through the route of Imam Malik (may Allah have mercy on him), from Yahya bin Sa'id, from Muhammad bin Ibrahim, from Abu Hazim, from Sayyiduna al-Bayadi (may Allah be pleased with him).
There is disagreement about the identity of this narrator Abu Hazim: in most narrations it is stated that he is the freed slave of Banu Ghifar and that his name is Dinar, whereas in this particular narration he is described as the freed slave of Banu Hudhayl. And Allah knows best.

It is narrated from Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) that he said (regarding the fixing of the Night of Decree): "The Night of Decree is the twenty-seventh night."

It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him) that he said: "The Night of Decree is the seventeenth night (of Ramadan); it is (the night of) that day spoken of as 'the day of decision between truth and falsehood, the day the two hosts (of believers and disbelievers) met' [Surah al-Anfal: 41]. I have no doubt about it, nor do I make any exception in it (that is, leave any room for doubt)."
This report makes clear that Sayyiduna Zayd bin Arqam (may Allah be pleased with him), in view of the occurrence of the Battle of Badr, held the night of the 17th of Ramadan to be the Night of Decree and firmly believed it.

It is narrated from Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) that he used to say (about this night): "It is the great night on the following day of which the Messenger of Allah (peace and blessings be upon him) met the people of Badr in battle." Concerning this, Allah, the Mighty and Majestic, says: "And (believe in) what (revelation and help) We sent down to Our servant on the Day of Decision, the day the two armies faced each other" [Surah al-Anfal: 41].
Imam Ja'far bin Burqan says: It has reached me that it was the sixteenth or seventeenth night of the blessed month of Ramadan.

It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "I saw the moon on the Night of Decree, and it appeared as though it were a piece of a large bowl."
Imam Abu Ya'la narrated this hadith in his Musnad; it mentions this particular shape of the moon, observed on this blessed night, as one of the visible signs of the Night of Decree.

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) came out one night intending to inform us of (the exact date of) the Night of Decree, and we had already been told about it; then he (peace and blessings be upon him) heard noise and clamour in the mosque, and that knowledge was taken away from (the memory of) him (peace and blessings be upon him).

It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that a man from the tribe of Juhaynah said: O Messenger of Allah, we are people who live in distant settlements, as you know, and we are not able to be present (in Madinah) for this whole month, so inform us about the Night of Decree. (The narrator says:) I said: O Messenger of Allah, is it the twenty-third night, when eight nights remain (before the month ends)? He (peace and blessings be upon him) said: "It is not so; this month can also fall short (that is, sometimes it has twenty-nine days), and it (the Night of Decree) is the night when seven nights remain."