Alms Tax: Selling the Crop After Zakat Becomes Obligatory
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1885
After zakat becomes obligatory on wheat, barley, dates, and grapes, if one sells the crop and trees, the seller must give the zakat on them; and in the event that he does so, it is not obligatory for the buyer.
-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)