On the authority of Mūsā ibn Abī Ṭalḥah, who said: “We have a document of Muʿādh from the Prophet—may Allah’s peace and blessings be upon him—that he only took charity from wheat, barley, raisins, and dates.”

Narrated by Aḥmad (no. 21989) and by al-Dāraquṭnī (no. 1913), from the ḥadīth of ʿUmar ibn al-Khaṭṭāb—may Allah be pleased with him—with the wording: “The Messenger of Allah—may Allah’s peace and blessings be upon him—only prescribed zakāh in these four: wheat, barley, raisins, and dates.”
Authenticated in Ṣaḥīḥ al-Jāmiʿ (no. 3584) and Silsilat al-Aḥādīth al-Ṣaḥīḥah (no. 879).

Brief Explanation of the Hadith

This ḥadīth clarifies that the zakāh on grains and fruits taken by the Prophet—may Allah’s peace and blessings be upon him—was from specific categories, namely: wheat, barley, dates, and raisins.
What is meant by “charity” here is the zakāh of crops and fruits, which is one-tenth or half of it, depending on the method of irrigation.
The intent is not to restrict zakāh to these specific items themselves; rather, the restriction here is one of shared attributes. Thus, everything that resembles them in being a staple food that is consumed, stored, and measured is included with them in ruling—such as rice, corn, millet, and the like—because the effective cause is the same.
As for that which is neither measured nor stored, there is no zakāh due upon it—such as fruits and vegetables—even if they come to be stored by modern means, due to the absence of the legally recognized attribute. These four categories were singled out for mention because they constituted the primary staple foods of that time and were the most commonly circulated and stored, with consideration given to the attainment of the niṣāb. This is due to his statement—may Allah’s peace and blessings be upon him—“There is no charity due on less than five awsuq (a specific measure of volume).”
And in the ḥadīth there is a clarification that the Prophetic Sunnah came to elucidate what is ambiguous in the Qurʾān and to detail what is stated therein in general terms.