Bukhari

Hadith Commentary:
Abdullah (radi Allahu anhu) was mounted on the camel. The Prophet (sallallahu alayhi wa sallam) purchased it from him while he was in that state, and then, out of kindness, gifted it back to Abdullah (radi Allahu anhu) while he was still mounted on it. From this, the heading of the chapter is established.

Hadith Commentary:
(1)
If someone gifts a camel to another person, and the one to whom it is gifted mounts it himself, then this gift is valid.
The Hanafis claim that it is not permissible to sell or gift something that is not in one’s possession.
Imam al-Bukhari rahimahullah states:
It is permissible to gift it even without possession, as long as the legal right of ownership has been established regarding it.
Abdullah ibn Umar radi Allahu anhu was mounted on a camel; the Messenger of Allah sallallahu alayhi wa sallam purchased it from him in that very state, and then, as a gesture of kindness, gifted it back to him. In this case, there was no physical possession, rather, the relinquishment of ownership between the person and the gifted camel constitutes possession.
(2)
It is also understood from this hadith that it is permissible to dispose of a purchased item before paying its price.
And Allah knows best.

Benefits and Issues:
Imam Bukhari rahimahullah has also mentioned this hadith in the chapter on gifts (hibah), so the commentator of Bukhari, Hafiz Ibn Hajar rahimahullah (773-852 AH), writes:
«وقال ابن بطال : مناسبة حديث ابن عمر للترجمة انه صلى الله عليه وسلم لو سأل عمر أن يهب البعير لابنه عبد الله لبادر إلى ذلك، لكنه لو فعل لم يكن عدلا بين بني عمر، فلذلك اشتراه صلى الله عليه وسلم منه، ثم وهبه لعبد الله، قال المهلب : وفي ذلك دلالة على أنه لا تلزم المعدلة فيما يهبه غير الاب لولد غيره وهو كما قال .»
"Allamah Ibn Battal rahimahullah says that the relevance of the narration of Sayyiduna Abdullah bin Umar radi Allahu anhuma to the chapter heading is that if the Prophet sallallahu alayhi wa sallam had told Sayyiduna Umar radi Allahu anhu to give a camel as a gift (hibah) to his son Abdullah, he would have complied immediately. However, in doing so, there would not have been justice among the sons of Sayyiduna Umar radi Allahu anhu. Therefore, the Prophet sallallahu alayhi wa sallam bought the camel and gave it as a gift (hibah) to Sayyiduna Abdullah bin Umar radi Allahu anhuma. Muhallab says: This hadith proves that if someone other than the father gives a gift (hibah) to another's children, then equality is not necessary in that. (Hafiz Ibn Hajar rahimahullah says:) This statement of his is absolutely correct." [فتح الباري شرح صحيح البخاري: 5/ 215]

It should be well remembered that if a person, during his lifetime, gives a share of his property to one or some of his sons and registers it in their names while depriving the others, then such a gift (hibah) is impermissible. In light of the aforementioned ahadith, it is obligatory to return such a gift (hibah).

Hadith Commentary:
(1)
Imam Bukhari rahimahullah did not mention the answer to the condition in the chapter heading because there is a difference of opinion among the jurists regarding this issue.
The situation is as follows: If someone purchases something and, before parting (from the gathering), immediately gifts it to someone else, and the seller does not object to the buyer, but rather, by remaining silent, expresses his consent to this action, then the sale is valid.
If the seller objects and is not pleased with this transaction, then the sale will not be valid, because for the contract of sale to be concluded, physical separation (tanaqud al-abdan) was necessary. However, in the aforementioned case, the seller’s silence causes the option of the gathering (khiyar al-majlis) to end.
In this hadith, only the mention of gifting (hibah) is present.
Imam Bukhari rahimahullah made an analogy between freeing a slave and gifting, because both are types of granting (giving away).

(2)
Ibn Battal said:
For those scholars who hold that a sale is not complete without physical separation, and who do not consider the buyer’s disposal (tasarruf) before separation to be permissible, this hadith is an argument against them.
(Fath al-Bari 4/424)

Benefit:
From this hadith, it is understood that the person to whom a gift (hadiyah) is given is the one entitled to it. If another person is present in that gathering, he cannot be considered entitled to that gift. Imam Bukhari rahimahullah has established a chapter on this hadith: “If something is given as a gift to someone while others are also sitting with him, then it should be given to the one who is more deserving.”