Bukhari

Hadith Commentary:
The truthfulness of the Messenger (sallallahu alayhi wa sallam) is established in this way: he described, through revelation, an incident occurring in a distant place even before news of it had reached him.
The truthfulness of the Messenger of Allah (sallallahu alayhi wa sallam).
If, as the people of innovation (ahl al-bid‘ah) claim, he had been the knower of the unseen (‘alim al-ghayb), then before setting out for the expedition of jihad, he would have stopped them and saved them from death. But he was not a knower of the unseen.
The noble verse: } : 188﴿وَلَوْ كُنْتُ أَعْلَمُ الْغَيْبَ لَاسْتَكْثَرْتُ مِنَ الْخَيْرِ﴾()
has precisely this meaning.
To inform by divine revelation (wahy ilahi) is a separate matter; to describe this as knowledge of the unseen (ghayb-dani) is the work of those who have not been granted even an atom of understanding or insight. It is clearly written in the books of jurisprudence (kutub fiqh) that whoever, believing the Prophet (sallallahu alayhi wa sallam) to be a knower of the unseen, makes him a witness over any matter, then this action of his leads him to disbelief (kufr).

Hadith Commentary:
➊
In the Battle of Mu'tah, the Muslims were fighting against the disbelievers. After the martyrdom of Abdullah bin Rawahah, Zayd bin Harithah and Ja'far al-Tayyar (radi Allahu anhuma) each took the flag in succession and were martyred.

➋
This hadith is also a proof of the Prophethood of the Messenger of Allah (sallallahu alayhi wa sallam), as, in accordance with his information, both of these noble companions drank from the cup of martyrdom. Its details will come under the discussion of the Battle of Mu'tah.

➌
In any case, through revelation (wahy), you (sallallahu alayhi wa sallam) described an event occurring at a distant place even before news of it had arrived.

According to the view of the people of innovation (ahl al-bid‘ah), if you (sallallahu alayhi wa sallam) had knowledge of the unseen (ghayb), you would have stopped them from going on the expedition of jihad beforehand and would have saved them from death. But you were not a knower of the unseen; conveying news of the unseen through divine revelation is another matter entirely.

To interpret this as knowledge of the unseen is the work of those who have not been granted even an atom’s worth of understanding or insight.

And Allah knows best.

Hadith Commentary: The Prophet (sallallahu alayhi wa sallam) did not participate in this expedition. He was giving all these reports to the Companions (radi Allahu anhum) while sitting in Madinah, and he came to know of all these circumstances through revelation (wahy). He was not one who possesses knowledge of the unseen (ghayb).

The details of the incident are as follows: In this battle, Ja'far (radi Allahu anhu) was holding the flag in his right hand. When the enemies cut off that hand, he took the flag in his left hand. The enemies cut that off as well, and he was martyred. The Prophet (sallallahu alayhi wa sallam) said that Allah Ta'ala granted him two wings like those of a bird in Paradise, and with them he flies wherever he wishes in Paradise. The word "Tayyar" means "one who flies." Because of this, he was called Ja'far al-Tayyar (radi Allahu anhu wa ardah).

Ja'far (radi Allahu anhu) had two sons named Abdullah and Muhammad. The Prophet (sallallahu alayhi wa sallam) showed great affection towards them. Musa ibn Uqbah mentioned in al-Maghazi that Ya'la ibn Umayyah came to the Prophet (sallallahu alayhi wa sallam) bringing news of the people of Mu'tah. The Prophet (sallallahu alayhi wa sallam) said to him: "If you wish, you may relate to me the condition of the people of Mu'tah, or else I myself will narrate to you their entire situation (which Allah has already informed me of through revelation before your arrival)."

Accordingly, the Prophet (sallallahu alayhi wa sallam) himself narrated their entire situation, and upon hearing this, Ya'la ibn Umayyah said: "By the One Who sent you as a Prophet, you have not left out a single letter in describing the condition of the people of Mu'tah. Your account is letter for letter accurate." (Qastallani)

Hadith Commentary:
1.
Khalid bin Walid (radi Allahu anhu) became Muslim at the time of the Treaty of Hudaybiyyah, and when he took up the Islamic banner after the martyrdom of Abdullah bin Rawahah (radi Allahu anhu), he ordered his army to retreat. They withdrew and then advanced again. The Romans thought that fresh reinforcements had reached them, which is why they were advancing. At that moment, a fierce battle took place, and ultimately victory came to the Muslims. The Messenger of Allah (sallallahu alayhi wa sallam) supplicated for him in these words: “O Allah! He is one of Your swords among Your swords, so help him.” (As-Sunan al-Kubra by an-Nasa’i: 5/69.) From that time, Khalid bin Walid (radi Allahu anhu) has been called Sayf Allah (the Sword of Allah).

2.
From this hadith, it is understood that it is permissible to appoint someone as a conditional commander or leader, and it is also clear that, when necessary, it is permissible to appoint a leader without the permission of the supreme authority. In this hadith, there is a clear virtue of Khalid bin Walid (radi Allahu anhu). (Fath al-Bari: 7/642.)

1879. Commentary:

➊ Announcing a death is permissible. Although in one hadith, announcing (na‘yu) has been prohibited—see: (Musnad Ahmad: 5/385). In reality, what is meant by this prohibition is the announcement of death in the manner of the pre-Islamic era of ignorance (jahiliyyah), which was done solely for pride and boasting, using grandiose and often false titles. Its purpose was not to inform, but to boast, and it was carried out with great ceremony and expense by professional announcers.

➋ This was a miracle of the Messenger of Allah (sallallahu alayhi wa sallam): the Companions were martyred in Syria (Sham), and he informed of their martyrdom in Madinah. The news of their martyrdom from Syria arrived later.