Bukhari

Hadith Commentary:
Some have translated it as: sometimes they would produce as much grain as could be loaded on a camel.
The translation of the chapter is derived from this, that we should also be included as partners in this grain.
By "food" (ta‘am), grains such as wheat, rice, etc., are meant.
It is also permissible to conduct business in partnership in these.
As mentioned in this hadith, there is reference to Abdullah ibn Hisham, a Companion (radi Allahu anhu) for whom the Prophet (sallallahu alayhi wa sallam) made supplication in his childhood, and due to the blessings of the Prophet’s supplications, Allah granted him abundant provision.
When his grandfather would go to the market to buy grain and such, he would take him along so that the blessings of the Prophet’s (sallallahu alayhi wa sallam) supplications would remain with him.
Sometimes, on the way, Abdullah ibn Umar and Abdullah ibn Zubair (radi Allahu anhuma) would meet them, and they too would request to be included as partners in this trade so that they could also benefit from the blessings of the Prophet’s (sallallahu alayhi wa sallam) supplications.
Thus, it often happened that all of them would return having earned much profit.
Upon this hadith, Hafiz (rahimahullah) says:
“And in the hadith: the stroking of a young child’s head, refraining from taking the pledge of allegiance (bay‘ah) from one who has not reached maturity, entering the market to seek livelihood, seeking blessings wherever they may be found, refutation of those who claim that abundance from lawful (halal) means is blameworthy, the eagerness of the Companions to bring their children to the Prophet (sallallahu alayhi wa sallam) to seek his blessings, and a sign of the Prophethood of the Prophet (sallallahu alayhi wa sallam) in the acceptance of his supplication for Abdullah ibn Hisham.”
That is, from this hadith it is established that stroking the head of young children with affection is a Sunnah of the Prophet (sallallahu alayhi wa sallam), and that it is also established not to take the pledge of allegiance from a minor, and that going to the market to seek livelihood is legislated, and that seeking blessings is established, wherever it may be found, and it is a refutation of those who consider striving for lawful sustenance to be blameworthy, and it is also established that most of the Companions would bring their children to the noble presence of the Prophet (sallallahu alayhi wa sallam) to obtain his supplications for their children, and the blessings that were obtained for Abdullah ibn Hisham through the Prophet’s supplication are among the important signs of the truthfulness of the Prophet (sallallahu alayhi wa sallam).
A similar incident is that of ‘Urwah al-Bariqi (radi Allahu anhu), who would go to the market and sometimes return with a profit of forty thousand, all due to the blessings of the supplications of the Prophet (sallallahu alayhi wa sallam).
Once, the Prophet (sallallahu alayhi wa sallam) gave him a dinar and sent him to buy a sacrificial animal, and he bought two sacrificial animals with that one dinar, and on the way sold one of them and recovered the dinar.
Then he presented the sacrificial animal to the Prophet (sallallahu alayhi wa sallam), along with the dinar gained as profit, and narrated the entire incident in detail. Upon hearing this, the Prophet (sallallahu alayhi wa sallam) was extremely pleased and supplicated for blessings in his business.
‘Allamah Qastallani (rahimahullah) says:
“And the correspondence of the hadith to the chapter is in his statement ‘include us as partners’ (ashrikna), for both of them requested partnership in the food he had purchased, and he accepted their request. They were all Companions, and nothing contrary to this has been transmitted from anyone else, so it is a proof. The majority hold the permissibility of partnership in everything that can be owned.”
(Qastallani)
That is, the correspondence of the hadith to the chapter is in the word “ashrikna.”
Both of these noble Companions requested to be included as partners in the purchased grain, and he accepted the request of both.
They were all Companions of the Prophet (sallallahu alayhi wa sallam), and nothing contrary to this has been reported from anyone else.
Thus, this is a proof, and the majority are of the opinion that partnership is permissible in everything that can be owned.

Hadith Commentary:
(1)
The position of the Maliki scholars is that partnership is not permissible in grain and produce. Imam Bukhari rahimahullah has established the aforementioned chapter heading in refutation of their view. From this narration, it is understood that partnership can occur in every owned item. It is also not necessary for the partnership to be on a half-share; rather, it depends on the mutual consent of the partners. It can be on a half, a third, or even a quarter share.

(2)
The relevance of the hadith to the chapter heading is as follows: Ibn Umar radi Allahu anhu and Ibn Zubair radi Allahu anhu would request Ibn Hisham radi Allahu anhu to include them as partners in the grain he had purchased, and he would accept their request and include them as partners in the grain. No opposition to this from anyone has been reported. And Allah knows best.