Bukhari

Hadith Commentary:
In this lengthy hadith, where the estimation of dates (khajoor) is mentioned, many other facts are also stated.
The expedition of Tabuk took place in 9 AH at such a time when the summer season was at its peak and the date harvest in Madinah was fully ripe.
Even so, the noble Companions (Sahabah kiram) demonstrated great self-sacrifice and, facing every hardship, participated in this long journey.
It was a matter of the frontier.
You (sallallahu alayhi wa sallam) stayed there for quite some time awaiting the enemy, but the enemy did not come forth for battle.
Rather, the Christian ruler of the nearby city of Aylah, Yuhanna bin Rubah, sent you a message of peace.
You (sallallahu alayhi wa sallam) maintained his rule for him.
Because your intention was never conquest of lands.
On the return journey, when the love for Madinah prompted you to hasten, you announced your intention to reach Madinah as quickly as possible.
When this pure city came into view, you (sallallahu alayhi wa sallam) became so pleased that you named this sacred city “Taba,”
which means pure and excellent.
Regarding Mount Uhud as well, you (sallallahu alayhi wa sallam) expressed your utmost love, and then you described the ranks of excellence among the tribes of the Ansar, giving the foremost rank to Banu Najjar.
It was among these people that your maternal relatives were, and when you first arrived in Madinah, these people, armed, came forth to welcome you.
Then, indeed, all the tribes of the Ansar are worthy of praise, who helped Islam with heart and soul in such a way that they will always be remembered in history.
Radi Allahu anhum wa radoo anhu.

Hadith Commentary:
(1)
The estimation of fruits on trees by an experienced person is called *kharṣ* (خرص). When dates or grapes ripen, the ruler sends an experienced estimator to the orchard to assess, by observation, how much dried fruit will be obtained from it. Then, based on this estimation, the obligation of ‘ushr (one-tenth) is determined. The expenses are deducted from the estimated amount.

(2)
According to the majority of scholars, it is valid to estimate dates and grapes, and it is permissible to collect ‘ushr according to this principle. However, the Hanafis do not accept this. According to them, the owner will pay ‘ushr on whatever amount comes into his possession, whether it is less or more than the estimation. But from the Islamic perspective, it is legislated for those who collect zakat to send people to estimate the grapes and fresh dates on the trees.

The Messenger of Allah (sallallahu alayhi wa sallam), after the conquest of Khaybar, sent Abdullah ibn Rawahah (radi Allahu anhu) to estimate the dates of the people of Khaybar.
(: Sunan Ibn Majah, Kitab al-Zakat, Hadith: 1820)

Hafiz Ibn Hajar (rahimahullah) has narrated a marfu‘ hadith from Sahih Ibn Hibban:
The Messenger of Allah (sallallahu alayhi wa sallam) said: When you estimate the fruits on the trees, then leave one-third from it; if you cannot leave one-third, then at least leave one-fourth.
(: Sunan Abi Dawud, Kitab al-Zakat, Hadith: 1605; Sunan al-Nasa’i, Kitab al-Zakat, Hadith: 2491)

It is narrated from ‘Attab ibn Asid (radi Allahu anhu) that the Messenger of Allah (sallallahu alayhi wa sallam) ordered that the zakat of grapes be estimated in the same way as the zakat of dates is estimated, and that the zakat of grapes be given from raisins just as the zakat of fresh dates is given from dried dates.
(: Jami‘ al-Tirmidhi, Kitab al-Zakat, Hadith: 644)

This means that the determination of the amount of zakat will be by estimation, but the payment of zakat will be from dried fruit. For other grains besides these, estimation is not valid.

And Allah knows best.