Bukhari

Hadith Commentary:
➊
Imam Bukhari rahimahullah established this chapter heading that a person's hair, after being separated from the body, remains pure; if it falls into water, the water does not become impure.
In this regard, he presented the statement of Ata bin Abi Rabah rahimahullah, who said that there is no harm in making thread and ropes from it.
According to the Hanafis, hair is indeed pure, but due to its sanctity and reverence, its use is not permitted.
Regarding the purity of hair, Imam Bukhari rahimahullah has now presented a marfu‘ narration,
in which the relics of the hair of the Messenger of Allah sallallahu alayhi wa sallam are mentioned.
The reasoning is that if hair were impure, why would it be kept as a relic? However, the objection to this reasoning is that to analogize the purity of ordinary human hair from the hair of the Messenger of Allah sallallahu alayhi wa sallam is an invalid analogy (qiyas ma‘ al-fariq), because the claim is general while the evidence is specific.
On this basis, this approach is incomplete.
But according to Imam Bukhari rahimahullah’s method of reasoning, it is valid, because there are two matters here: one is the purity of hair, and the other is seeking blessing (tabarruk) from it.
Now, the claim that the purity of the hair of the Messenger of Allah sallallahu alayhi wa sallam is his specific characteristic requires evidence for such specificity.
The Messenger of Allah sallallahu alayhi wa sallam did not mention such a specificity even at the time of distribution, so this means that the hair of all humans, after being separated from the body, remains pure.
As for the matter of seeking blessing, specific tabarruk will remain exclusive to the Messenger of Allah sallallahu alayhi wa sallam.

➋
Those who claim to be people of reflection (tadabbur) have made this assertion to cast doubt upon the hadiths:
“The chapter that the Imam established was about the water with which hair is washed or in which a dog has dipped its mouth; there is no such mention in the narrations.” (Tadabbur Hadith: 1/274)
Firstly, the purpose of Imam Bukhari rahimahullah is to state the legal ruling regarding those things which occasionally fall into water: do such things, when falling into water, render it impure or not? Here, the mention of water has come incidentally due to the context of occurrence; the main objective is not to discuss issues related to water, because those will be discussed later.
Since these things generally fall into water, water is mentioned here; otherwise, these things also fall into food, milk, etc., just as they do into water.
Imam Bukhari rahimahullah has discussed the issue of hair in this chapter heading, whether it falls into water or into food.
Secondly, the mention of hair falling or being placed in water is found in other narrations. For example, Abdullah bin Muhaib says that his family sent him with a bowl of water to Umm al-Mu’minin Umm Salamah radi Allahu anha, because she had preserved the blessed hair of the Messenger of Allah sallallahu alayhi wa sallam in a beautiful silver container.
She would place them in water and stir it, then that water would be given to a person afflicted with the evil eye or fever to drink.
At that time, I saw red-colored blessed hair in the container.
(Sahih al-Bukhari, Kitab al-Libas, Hadith: 5896)
As for the matter of a dog dipping its mouth into water, Imam Bukhari rahimahullah has established a separate, independent chapter for this as a sub-chapter and has also mentioned narrations regarding it.
Such passionate expressions of devotion regarding the blessed hair of the Messenger of Allah sallallahu alayhi wa sallam were contrary to the alleged rationalism of the people of “tadabbur,” so they mocked Talhah radi Allahu anhu as being “emotional and excitable” because he preserved the Prophet’s hair.
And as for those narrations in which it is mentioned that the Messenger of Allah sallallahu alayhi wa sallam himself appointed him to distribute the hair and granted him the blessed hair for this purpose, all such narrations are, in their view, questionable.
(Tadabbur Hadith: 1/273)

➌
This beautiful devotion to the hair of the Messenger of Allah sallallahu alayhi wa sallam was not exclusive to Abu Talhah radi Allahu anhu; rather, all the noble Companions radi Allahu anhum had similar feelings. Thus, Anas radi Allahu anhu says:
“I saw the Messenger of Allah sallallahu alayhi wa sallam while the barber was shaving his blessed head, and the Companions radi Allahu anhum were around him, desiring that not a single hair of his should fall to the ground, but rather fall into someone’s hand.”
(Sahih Muslim, Kitab al-Fada’il, Hadith: 6043(2325))
In fact, the statement of Urwah bin Mas‘ud is even more astonishing, because he had not yet become Muslim. He describes the love and devotion of the Companions radi Allahu anhum in these words:
“When the Messenger of Allah sallallahu alayhi wa sallam performs ablution (wudu), his Companions radi Allahu anhum rush to take the water that falls to the ground; when he spits, they hasten to catch it and rub it on their hands and faces, and whenever a hair of his falls, they immediately take it.”
(Sahih al-Bukhari, Kitab al-Shurut, Hadith: 2731, 2732; Musnad Ahmad: 4/324)
Further details on this issue will come in Kitab al-Libas.