Bukhari

Hadith Commentary:
The meaning is that in the future, there will be many Muslims who will be in need.
If I continue to distribute all the conquered lands among the warriors (ghazis), then the needy Muslims of the future will be left deprived.
This was stated by Umar (radi Allahu anhu) at the time when the land of Sawad was conquered.

Hadith Commentary:
(1)
During the caliphate of Umar radi Allahu anhu, when the regions of Iran and Iraq were conquered, he did not distribute the lands there among the warriors (mujahideen); rather, he allowed the lands to remain with the local dhimmis as sharecroppers (muzara‘ah). However, the Muslims would benefit from their produce. He kept those lands as government property because if the lands of the conquered territories had been distributed, then where would the people who came later go?

(2)
Until the conquest of Khaybar, the Messenger of Allah sallallahu alayhi wa sallam distributed all conquered lands among the warriors (mujahideen), so why did Umar radi Allahu anhu withhold the lands of Syria for the state? Imam Bukhari rahimahullah, in the chapter heading (tarjamat al-bab), has brought the hadith of Umar radi Allahu anhu to answer this objection: that the caliph has the right to make changes in view of the public interest (maslahah), just as the Messenger of Allah sallallahu alayhi wa sallam dedicated Umar’s radi Allahu anhu charity (sadaqah) for the benefit of the Muslims as state property, similarly Umar radi Allahu anhu gave the lands of Syria on sharecropping (muzara‘ah) for the benefit of the Muslims.

(3)
When waqf (endowed) lands can be given on sharecropping (muzara‘ah), then privately owned lands can also be given, because the ruling for both is the same.

Hadith Commentary:

What Umar (radi Allahu anhu) had said came to pass: in later times, Muslims increased greatly in number and spread throughout the regions of the world. Thus, the conquered lands were distributed by them according to the principles of Islamic law (shar‘i rules) in the same manner, and the statement of Umar (radi Allahu anhu) proved to be correct.

In the hadith, the word "baban" appears.
...
The word is written with two ba’s, the second ba being mushaddad (doubled).
Abu Ubayd (rahimahullah) says: I think this word is not of Arabic origin.
Zuhri (rahimahullah) says: This is a word from the Yemeni language, which did not become well-known among the Arabs.
The meaning of "baban" is: equally, in one manner and one way; and some have said it means "poor" or "needy."
(Wahidi)

Hadith Commentary: The meaning of the statement of Umar (radi Allahu anhu) is that, had I not been concerned about those people who will become Muslims in the future and who will be utterly destitute, I would have distributed all the lands that were being conquered as estates among the Muslims, and would not have kept anything as state property, the revenue of which is deposited in the public treasury (Bayt al-Mal). However, I am concerned about those people who will become Muslims in the future—if they are needy, then nothing would remain for their subsistence.
Therefore, I keep the acquisition of land in the treasury so that it may benefit such Muslims in the future.

Hadith Commentary:
Movable items have always been distributed among the mujahideen, but regarding immovable land, the Imam has the authority either to distribute it or to keep it for public welfare (masalih ‘ammah).

‘Umar radi Allahu anhu, exercising his discretionary authority, did not distribute the conquered land.

An objection may arise: Did ‘Umar radi Allahu anhu have the right to withhold the share of the ghanimeen (those entitled to war booty)? The answer is that he satisfied the ghanimeen by giving them gifts and so forth, and then dedicated the conquered land as a waqf (endowment) for the Muslims, lest miserliness should prevail among the people and nothing be left for future generations.

‘Allamah ‘Ayni rahimahullah has written that there is consensus (ijma‘) of the Ummah on this matter: if at any time the Imam deems it appropriate to distribute the land and wishes to do so at his discretion, he may distribute the conquered territory.

(Fath al-Bari: 7/612.)

In any case, ‘Umar radi Allahu anhu did not distribute the land of Iraq, but rather dedicated it as a waqf for public welfare.

Hadith Commentary:
Most of the imams have given the legal verdict that, regarding conquered lands, the ruler (imam) has the authority—he may either distribute them or leave them as land subject to kharaj (land tax).
But this kharaj, according to Islamic principles, should be spent only on Muslims—that is, for the care of the needy, orphans, the preparation of equipment and provisions for jihad. In short, the revenues of the country are not the personal property of the king.
Rather, it is the wealth of the general Muslims and the warriors (ghazis).
The king, too, may take his expenses from it only in the capacity of a soldier.
This is the Shari‘ah system, but alas, today it is absent from most Islamic countries.
So weep for Islam, if you are to weep.

Hadith Commentary:
➊
The chapter heading established by Imam Bukhari rahimahullah is, in fact, a statement of Umar radi Allahu anhu, which has been transmitted with an authentic chain in the Musannaf of Abd al-Razzaq, that Umar radi Allahu anhu wrote to Ammar radi Allahu anhu that the one entitled to the spoils of war (ghanimah) is the fighter who participates in the battlefield.
( : al-Musannaf li-Abd al-Razzaq: 5/302)

➋
This hadith also corresponds to the chapter heading, because the Messenger of Allah sallallahu alayhi wa sallam, upon the conquest of Khaybar, distributed the conquered land among the fighters (mujahideen). However, Umar radi Allahu anhu, due to an external expediency, instead of distributing the conquered lands and regions, dedicated them as endowments (waqf), and the produce obtained from them was spent on the needs of the Muslims.
( : Fath al-Bari: 6/270)

The commentator of Bukhari, Ibn Munir, writes:
According to Imam Bukhari rahimahullah, it is more appropriate to distribute the conquered lands, because the Muslims who came later did not participate in the battlefield, so that the lands should be dedicated as endowments for them.

Our inclination is that Imam Bukhari rahimahullah wishes to reconcile the statement of Umar radi Allahu anhu—“The spoils of war are the right of the one who was present in the battle”—and his action—he did not distribute the conquered regions among the fighters—in such a way that the land is dedicated as an endowment (waqf), and the remaining spoils of war are distributed among the fighters who participated in the battle.
( : Fath al-Bari: 6/271)

In reality, the practical stance of Umar radi Allahu anhu is based on those verses of Surah al-Hashr in which the rightful recipients of the fay’ wealth are mentioned.
Among them, first the needy emigrants (muhajirun) are mentioned, then the Ansar who show selflessness, and thirdly, the later-coming people of Islam.
( , : al-Hashr: 8, 10)

If the lands of the conquered settlements had been distributed among the conquerors, then nothing would have remained for the Muslims who came later, whereas the Noble Qur’an has also declared them to be entitled. Therefore, Umar radi Allahu anhu, instead of distributing the conquered lands, dedicated them as endowments (waqf).
And Allah knows best.

Benefits and Issues:
Approximately half of Khaybar, which was obtained as spoils of war (ghanimah), was distributed after extracting the khums (one-fifth share).
This was a very large portion.
The indication of Umar radi Allahu anhu is towards this.
In addition, in the Islamic state, according to circumstances, such a fund and endowment (waqf) should be preserved,
which can be utilized for the collective needs of the Muslims.