Bukhari

Hadith Commentary:
Hazrat Umar radi Allahu anhu said this so that, with the destruction of Ibn Sayyad, the world would be cleansed of him and there would no longer remain any fear of the Dajjal in the future.

The relevance of this hadith to the Book of Qadar (Divine Decree) is as follows: The Prophet sallallahu alayhi wa sallam said, "If he is the Dajjal, then you will not be able to kill him, because Allah has decreed in destiny that he will emerge near the Day of Judgment, misguide people, and ultimately be killed at the hands of Hazrat Isa alayhis salam."
It cannot happen contrary to what is decreed.

In reality, considering the literal meaning of the word "Dajjal," Ibn Sayyad was also one of the individuals in the list of dajjals; in all his actions, there was complete involvement of deceit and trickery. Such people have been numerous in the Ummah, are present even today, and will continue to appear in the future. They have been called "dajjals" and "liars" (dajjalun kadhdhābūn).

Hadith Commentary:
(1)
The meaning of the statement of the Messenger of Allah (sallallahu alayhi wa sallam) was that if this is indeed the same Dajjal whose emergence and misguidance of people is in the knowledge of Allah, then your Creator and Master will not grant you the power to kill him; rather, He will intervene and prevent it.
If He were to grant you the power to kill him, then there would be a deficiency in the knowledge of Allah, which is impossible.
The purpose is that the decree of destiny (qadar) is absolute and unchangeable.
If it were possible for it to be averted for anyone, then today Umar (radi Allahu anhu) would not have been disappointed by being told that you cannot kill this boy (Ibn Sayyad).
(2)
The return of Isa (alayhis salam) to this world and his coming to kill the Dajjal is among those decisive decrees of destiny that are unalterable.
Here, even the strength and valor of someone like Umar (radi Allahu anhu) is of no avail.
These are secrets of divine power; if He were to state any condition or restriction and thereby defer His decision, then today this Ummah would have been delivered from those terrifying calamities whose very thought makes one’s hair stand on end. But that Self-Sufficient Being has no concern for this.
(3)
After this clarification, not even a whisper of doubt arose in the heart of Umar (radi Allahu anhu) to say, “Let me at least try and see whether I have the power to kill him or not.”
In any case, just as the killing of the Dajjal has been decreed in destiny, so too has his killer been decreed. It is impossible that he should be killed, but by some other means; he will certainly be killed, but only by the means that has been decreed for him.
And Allah knows best.

Hadith Commentary:
Ibn Sayyad was a Jewish boy in Madinah who used to make grand claims, saying that revelation also descends upon him.
In reality, he was possessed by a devil.
He would often remain in a semi-conscious state and utter insane things.
The Messenger of Allah (sallallahu alayhi wa sallam) once wished to secretly listen to his ramblings so that he would not see him.
This very incident is mentioned here, and it is from this that the Imam (rahimahullah) has established the chapter heading.

Hadith Commentary:
(1)
If someone observes or hears an incident secretly, will his testimony be valid or not? Some scholars are of the opinion that a person who secretly investigates someone’s circumstances has his integrity (adala) compromised, therefore his testimony will not be accepted. However, sometimes such action becomes necessary in order to acquire accurate knowledge of the situation. For example, Ibn Sayyad used to secretly commit acts of disobedience and deception; in the case of such people, it is permissible to listen to their speech by any means so that, after full clarification, a ruling may be made. Accordingly, the Messenger of Allah (sallallahu alayhi wa sallam) devised a plan to secretly ascertain the circumstances of Ibn Sayyad and listened to his conversation in secret. He also said:
“If his mother had not warned him, several matters concerning him would have been revealed.”

(2)
If the testimony of one who listens secretly is not accepted, then the department of investigation and its functioning would become useless. Now the world has advanced to such an extent that a small device can be placed at any location, which records all the conversation of those present. Such testimony will be accepted; however, it may be subject to cross-examination so that no immoral or wicked person may take undue advantage of it. Where there is a risk of confusion regarding voices, complete reliance will not be placed on such testimony that is based solely on hearing. In any case, the right to cross-examine in such matters should remain preserved so that the reality of the situation can be ascertained.

Explanation:
1:
You should await the day when the sky will bring forth an evident smoke.

2:
Some of the noble Companions (radi Allahu anhum) thought that this was the very Masih al-Dajjal (Antichrist) whose appearance near the end of times had been foretold. However, from the narration of Fatimah bint Qays (radi Allahu anha), in which Tamim al-Dari (radi Allahu anhu) described the events of his sea journey, it becomes clear with certainty that Ibn Sayyad is not the greater Dajjal (Dajjal al-Akbar), but rather someone else. Ibn Sayyad is merely one of those impostors (dajjals) and great liars (kadhdhabin) whose appearance the Messenger of Allah (sallallahu alayhi wa sallam) had foretold, and most of them have already appeared. As for those Companions who, with conviction, swore oaths and called Ibn Sayyad the Dajjal—even in the presence of the Prophet (sallallahu alayhi wa sallam), and he remained silent—then all of these statements occurred before the incident involving Tamim al-Dari.

Benefits and Issues:
Allamah Ibn al-Athir writes in al-Nihayah that this was a Jew who used to associate and mix with them.
His name has been mentioned as Safu.
He possessed knowledge of soothsaying and magic, and in his time he was a test for the righteous servants of Allah, so that whoever was to be destroyed would be destroyed upon evidence, and whoever was to remain alive would remain alive upon evidence.
Most say that he died in Madinah, and it has also been said that at the time of the incident of Hira, he was found missing and was never found again.
And Allah knows best.

Takhrij:
«أخرجه الدار قطني: 3 /252 وسنده ضعيف، وللحديث شواهد عند الطحاوي في معاني الآثار:2 /150 وغيره، وعلقه البخاري، الجنائز، قبل حديث:1354.»©Explanation:
➊ In this hadith, there is both information and prophecy: that Islam has come to remain dominant, not to be subdued. Therefore, the people of Islam should strive, both ideologically and practically, to keep it dominant. They should propagate and spread Islam correctly, and first mold their own practical lives according to it, so that non-Muslims, being influenced by their actions, character, and manners, may enter the fold of Islam.

➋ This hadith has been mentioned as a prelude and introduction to a truce (sulh), that in mutual reconciliation, even if, hypothetically, any condition apparently seems to be against the interests of the one who professes Islam, there is no need to be worried or anxious.

➌ Islam is the religion favored by Allah. He will always keep it exalted, superior, and dominant. If its followers act according to it, they will be successful, and Allah, the Exalted, will grant help and support to Islam and the people of Islam.

➍ Islam’s dominance in terms of proofs and evidences over all others is an established fact.

© Hadith Narrator:
«حضرت عائذ بن عمرو مزنی رضی اللہ عنہ » Abu Hubayrah was his kunyah. He settled in Basrah. He was among the most righteous of the Companions (radi Allahu anhum). He was present at the Pledge of Ridwan (Bay‘at al-Ridwan). He passed away during the era of Yazid ibn Mu‘awiyah.