As for the legal principles that seem to run counter to ocular estimation (kharṣ):
They argue that it resembles muzābanah—prohibited by the Law—namely, selling fruit still hanging on the palms for an already-measured amount of harvested fruit. It is also akin to selling fresh dates for dried dates on deferred payment, a transaction that combines both forbidden excess and delay—two foundational causes of ribā. Seeing this, and noting that the estimation performed for the people of Khaybar was not for Zakāt, since they were not liable for Zakāt, the Kufan jurists said: “It is possible that it was nothing more than an appraisal to determine how much fruit each group possessed.”

The Qāḍī remarks:
According to Mālik’s report, the apparent purpose was division of the crop, for it is related that when ʿAbd Allāh ibn Rawāḥah finished the estimation he would say, “If you wish, it is yours; if you wish, it is mine”—meaning the division of the fruit, not of the grain.

On the other hand, the ḥadīth of ʿĀʾishah, transmitted by Abū Dāwūd, indicates that the estimation was to determine the obligatory share due from them. She said—while recounting the events of Khaybar—“The Prophet, peace and blessings be upon him, used to send ʿAbd Allāh ibn Rawāḥah to the Jews of Khaybar, and he would estimate their date-palms when the fruit ripened, before any of it was eaten.”

The Two Shaykhs (al-Bukhārī and Muslim) did not include the report about estimating the fruit. In any case, kharṣ remains an exception to those general principles—so long as it is established that it was a ruling from the Prophet, peace be upon him, directed to the Muslims. A judgment confined to people under covenant does not automatically become a universal ruling for the Muslims without further proof. Allah knows best.

Had the ḥadīth of ʿAttāb ibn Asīd been sound, the permissibility of kharṣ would be unequivocal—Allah knows best. That ḥadīth relates that he said: “The Messenger of Allah—peace and blessings be upon him—commanded me to estimate the grapes and to take their Zakāt as raisins, just as the Zakāt of the date-palms is taken in dates.”

The report of ʿAttāb has been challenged, because its transmitter from him is Saʿīd ibn al-Musayyab, who never heard from ʿAttāb. For that reason Dāʾūd did not allow the estimation of grapes. Those who hold Zakāt to be obligatory on olives likewise disagree over whether olives may be estimated.

Their dispute turns on whether olives may be analogically compared to date-palms and grapes: everyone agrees that the Zakāt taken from palms is dates, not fresh rutab, and from vines is raisins, not the grapes themselves. Similarly, according to those who require Zakāt on olives, what is taken is the oil, not the berries, by analogy with dates and raisins.

Mālik said with regard to grapes that cannot be dried into raisins and olives that are not pressed for oil: “In my view, Zakāt should be taken from them in their berry form.”